Abstract:
A broadband wireless access apparatus that can be separated to improve its portability and mobility and its frequency interference avoiding method are disclosed. The broadband wireless access device includes: a main body unit having a power and multi-network management function; an antenna cradle rotatably combined with the main body unit; and a detachable (separation-type) wireless access device detachably attached to the antenna cradle.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to Korean Application No. 10-2007-0140933 filed in Korea on Dec. 28, 2007, the entire contents of which is hereby incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a broadband wireless access apparatus that can be separated to improve its portability and mobility and its frequency interference avoiding method. 
         [0004]    2. Description of the Related Art 
         [0005]    Recently, user demands for a broadband wireless LAN service or a mobile Internet service allowing data communication by a connection to the Internet and long distance communication such as a mobile phone are on the rise. 
         [0006]    For example, WiBro (Wireless Broadband) is a mobile Internet service, which is advantageous in terms of unit costs in spite of its drawbacks that the number of base stations (about 1.2 to 1.5 times) or movable speed (about 60 km) is relatively bad compared with the EV-DO (Evolution Data Only) service currently available for the CDM mobile phone. 
         [0007]    Wimax, started from a somewhat different phase from the WiBro, is a service aimed to overcome the shortcomings of the existing wireless LAN that there is much limitation in availability because of its short arrival distance of tens of meters although a large number of access points are installed. In this sense, the Wimax may be considered a wireless LAN that has a hugely extended distance and speed. 
         [0008]    In order to stably use the mobile Internet service with quality wireless performance indoors, a broadband wireless access device having high wireless performance should be installed. However, the related art broadband wireless access device as shown in  FIG. 1  is too high and voluminous overall to be stably used. In addition, because it has been developed as a fixed device, its portability and mobility are not good. 
         [0009]      FIG. 1  is a perspective view of the related art broadband wireless access device, which includes a main body  110  of the broadband wireless access device, various types of antennas  120  combined with the main body  110 , and a supconnection terminal 130  for making the main body stand. 
         [0010]    The main body  110  of the broadband wireless access device includes a connection terminal 111  formed at one side thereof to connect a power source and a fixed line network, and a terminal  113  formed at another side to connect a short range wireless communication antenna  112  and a terminal  114  formed at still another side to connect a plurality of broadband wireless communication antennas. As the broadband wireless communication antennas, a plurality of straight dipole antennas  121  may be connected or a box-shaped directional antenna  122  may be connected. 
         [0011]    As shown in  FIG. 1 , when the antenna is combined to the related art broadband wireless access device, the height is increased, degrading the stability and increasing the overall volume to cause restriction in the mobility and portability. 
       SUMMARY OF THE INVENTION 
       [0012]    Accordingly, one object of the present invention is to address the above-noted and other problems. 
         [0013]    Another object of the present invention is to provide an indoor broadband wireless access device (i.e., customer premise equipment) having a main body in the shape of a supconnection terminal(stand) allowing an antenna to be combined thereto. 
         [0014]    Still another object of the present invention is to provide a detachable wireless access device that can be detachably attached to an indoor broadband wireless access device. 
         [0015]    Yet another object of the present invention is to provide a method for providing or performing two wireless access services using close frequency bands in a single apparatus without causing a mutual frequency interference. 
         [0016]    To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, the present invention provides in one aspect a broadband wireless access device including: a main body unit having a power and multi-network management function; an antenna cradle rotatably combined with the main body unit; and a detachable (separation-type) wireless access device detachably attached to the antenna cradle. 
         [0017]    The main body unit may be configured to supply power to the antenna cradle and the detachable wireless access device, connect and manage a plurality of Ethernet lines including a short-range wireless communication (near field communication) service, provide a VoIP call service by connecting an analog call, and control an overall operation of the broadband wireless access device in association with the respective elements and the detachable wireless access device. 
         [0018]    The antenna cradle may include: a plurality of transmission/reception antennas for broadband wireless communication; a plurality of switches that selectively switch switching the antennas; a plurality of band filters that filter broadband radio signals transmitted/received via the antennas; a high output power amplifier that amplifies a broadband radio signal to be outputted to a transmission antenna among the antennas; and a plurality of connection terminals that connect the detachable wireless access device, an RF signal path and a control signal. 
         [0019]    The detachable wireless access device may include: a plurality of transmission/reception antennas that transmit/receive signals filtered by a plurality of band filters; a power amplifier that amplifies a broadband radio signal to be transmitted to a transmission antenna; an RF signal processing unit that processes a broadband radio signal transmitted/received via the antennas; and a broadband communication controller that controls the signal processing operation and controls an operation for a wireless radio access by communicating with the main body unit and the antenna cradle. 
         [0020]    The indoor broadband wireless access device according to the present invention has the advantage that because the main body unit is configured as the shape of a supconnection terminal that can be combined with antennas, the height and volume can be reduced and the stability can be improved. 
         [0021]    In addition, because the detachable wireless access device can be attached to or detached from the indoor broadband wireless access device, the mobility and portability can be improved. 
         [0022]    Moreover, when two types of wireless access services using close frequency bands are performed, they are not interfered by mutual frequencies, increasing the utilization of frequency resources. 
         [0023]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by illustration only, and thus are not limitative of the present invention, and wherein: 
           [0025]      FIG. 1  is a perspective view of a broadband wireless access device according to the related art; 
           [0026]      FIG. 2A  is a front perspective view of a broadband wireless access device according to an embodiment of the present invention; 
           [0027]      FIG. 2B  is a rear perspective view of the broadband wireless access device according to an embodiment of the present invention; 
           [0028]      FIG. 3  is a block diagram showing an internal configuration of the broadband wireless access device according to an embodiment of the present invention; 
           [0029]      FIG. 4  is a view for showing a combination of the broadband wireless access device and a detachable wireless access device according to an embodiment of the present invention; 
           [0030]      FIG. 5  is a view showing a configuration of a connection terminal for connecting the broadband wireless access device and the detachable wireless access device according to an embodiment of the present invention; 
           [0031]      FIGS. 6A and 6B  are flow charts illustrating the process of a method for positively avoiding an interference of the broadband wireless access device according to an embodiment of the present invention; and 
           [0032]      FIGS. 7A and 7B  are flow charts illustrating the process of a method for negatively avoiding an interference of the broadband wireless access device according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In describing the present invention, if a detailed explanation for a related known function or construction is considered to unnecessarily divert the gist of the present invention, such explanation has been omitted but would be understood by those skilled in the art. In describing the present invention with reference to the accompanying drawings, the like reference numerals are used for the elements performing the like function. 
         [0034]    The mobile terminal according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings. 
         [0035]      FIG. 2A  is a front perspective view of a broadband wireless access device according to an embodiment of the present invention, and  FIG. 2B  is a rear perspective view of the broadband wireless access device according to an embodiment of the present invention. 
         [0036]    As shown in  FIGS. 2A and 2B , the broadband wireless access device according to an embodiment of the present invention includes: a main body unit  210  configured as a supconnection terminal (pedestal, prop), an antenna cradle  220  rotatably combined on the main body unit  210 , and a detachable wireless access device  230  that can be attached to or detached from the antenna cradle  210 . 
         [0037]    The main body unit  210 , the antenna cradle  220 , and the detachable wireless access device  230  are not limited to the configuration as shown in  FIGS. 2A and 2B  but may have various configurations. 
         [0038]    The main body unit  210  includes an indicator unit  211  formed on a front side and indicating various operation states, and an interface unit  212  formed on a rear side and connecting an operation power source and a plurality network lines and telephone lines. 
         [0039]    The antenna cradle  220  includes a plurality of antennas therein, and a plurality of switches, a filter, a power amplifier, or the like for selecting an antenna to transmit/receive a signal. The antenna cradle  220  also includes a coupling unit  221  formed on a front surface (or rear surface) to couple the detachable wireless access device  230 . Further, the antenna cradle  220  may be configured to be rotatable 180° clockwise or counterclockwise in order to change an antenna direction angle. 
         [0040]    The coupling unit  221  may have a recess form so that although the detachable wireless access device  230  is attached thereto, it may not be protruded from the antenna cradle  220 . In this case, the recess may be configured according to the shape of the wireless access device  230 , and in order to easily attach or detach the detachable wireless access device  230 , a recess to allow the user&#39;s finger to be received therein may be formed at an upper portion or left/right portion of the recess in which the wireless access device is combined. In addition, the coupling unit  221  includes a locking unit  229  in order to firmly fix the detachable wireless access device  230  so that the detachable wireless access device  230  cannot be shaken or released, when the detachable wireless access device  230  is attached to the antenna cradle  220 . 
         [0041]    The coupling unit  221  may include a plurality of connection terminals or connectors  222  to  224  for electrically connecting the detachable wireless access device  230  to the antenna cradle  220  and the main body unit  210 . The connection terminals (or connectors) may include a connector  224  in the same of a USB connector. The connector  224  in the shape of the USB connector may be configured to be rotated at a certain angle toward a front side of the antenna coupling unit  220  to allow the detachable wireless access device  230  to be easily attached or detached. 
         [0042]    The functional operation of the broadband wireless access device will now be described. 
         [0043]    First, when the detachable wireless access device  230  is attached to the antenna cradle  220 , the antenna cradle  220  interrupts an antenna connection within the detachable wireless access device  230 . This is because an internal mobile switch (not shown of the antenna cradle  220  switches an RF signal path from an internal antenna  236   a  of the detachable wireless access device  230  to an antenna  228  of the antenna cradle  220 . Accordingly, the detachable wireless access device  230  is connected with the internal antenna  228  of the antenna cradle  220  via the RF path. 
         [0044]    The antenna cradle  220  includes a plurality of antennas  228   a  to  228   n,  so it can obtain a space diversity gain according to switching of the antennas, a high output by the power amplifier and effectively remove a signal interference by a short-range wireless LAN (e.g., WiFi) provided in the main body unit  210  via a BPF (Band Pass Filter or the like. 
         [0045]    When the detachable wireless access device  230  is attached on the antenna cradle  220 , the main body unit  210  may perform data communication by controlling a host processor  215 . in this case, the data communication method follows a radio communication scheme provided in the detachable wireless access device  230  that may include a broadband radio communication scheme including WiMax, OFDM (Orthogonal Frequency Division Multiplexing) method, or a compatible method. 
         [0046]    The detachable wireless access device  230  may include a power switch  233  provided on a surface exposed when the detachable wireless access device  230  is attached on the antenna cradle  220 . The power switch  233  may have an indicator function based on a backlight and display a state when power is applied or when the power switch operates, as a backlight. Of course, the indicator may use a light emitting element and may be configured at a different position from the position as shown in the drawing. 
         [0047]    The power switch  233  performs a switching function of resetting, a network connection, a network release and a power ON/OFF. 
         [0048]    For example, according to the switching method, hardware of the detachable wireless access device  230  may be reset by pressing the power switch  233  once for a short time. 
         [0049]    When the detachable wireless access device  230  is connected with the main body unit  210 , the main body unit  210  automatically recognizes the detachable wireless access device  230  to perform initialization. When the initialization operation is completed, the detachable wireless access device  230  is available for being connected with a wireless network, and at this time, the power switch  233  may indicate the corresponding state via the indicator. 
         [0050]    If the power switch  233  is pressed for more than a certain time, power of the detachable wireless access device  230  may be turned off. In this case, before the power is turned off, the broadband communication controller  232  of the detachable wireless access device transmits a connection release message to a base station. A host processor  215  of the main body unit  210  may check the turn-off state of the detachable wireless access device  230  and indicate the fact that the detachable wireless access device  230  does not operate via the indicator unit  211 . 
         [0051]      FIG. 3  is a block diagram showing an internal configuration of the broadband wireless access device according to an embodiment of the present invention. 
         [0052]    With reference to  FIG. 3 , the main body unit  210  includes a power supply unit  218  that receives external power and supplies operation power to the antenna cradle  220  and the detachable wireless access device  230 , an Ethernet controller  213  that manages a connector RJ-45 for connecting a plurality of Ethernet lines and the plurality of Ethernets, a codec/subscriber audio interface unit  214  that connects a connector an RJ-11 for connecting a telephone line and a telephone to a computer or a VoIP terminal to allow performing of a high quality VoIP call, a VoIP processor  216  that performs a VoIP service via the codec/subscriber audio interface unit  214 , a short-range wireless communication processor  217  that performs short-range wireless communication service including a WLAN or WiFi, and a host processor  215  that controls the overall operation of the broadband wireless access device in association with the processors and the detachable wireless access device  230 . 
         [0053]    Here, if the processor is implemented as hardware, it may be implemented by using at least one of electric units such as ASICs (application specific integrated circuits), DSPs (digital signal processors), DSPDs (digital signal processing devices), PLDs (programmable logic devices), FPGAs (field programmable gate arrays), processors, controllers, micro-controllers, and microprocessors. 
         [0054]    The antenna cradle  220  includes an antenna unit  228  including a plurality of transmission/reception antennas  228   a  to  228   n  for broadband wireless communication, an antenna switching unit  227  including a plurality of switches  227   a  and  227   b  that selectively switch the antennas of the antenna unit  228  under the control of the broadband communication controller  232  of the detachable wireless access device  230 , a filter unit  226  including a plurality of band filters for canceling noise from an RF signal transmitted to/received from an antenna connected via the antenna switching unit  227 , a high output power amplifier  225  that amplifies an RF signal to be outputted to a transmission antenna among the antennas, and a plurality of connection terminals  222  to  224  that connect the antenna unit  228  and the detachable wireless access device  230  to establish an RF signal path and a control signal path. 
         [0055]    The antenna cradle  220  includes the plurality of (N number of) high gain antennas  228   a  to  228   n,  and the high output power amplifier  225  for amplifying and outputting a transmission signal when connected with the detachable wireless access device  230 . 
         [0056]    The antenna cradle  220  further includes band filters  226   a  to  226   c  having high skirt characteristics at every RF signal path to restrain an interference by a short-range radio signal (WiFi) from the main body unit. For example, a stop band of the respective band filters  226   a  to  226   c  may be 2.4 GHz to 2.472 GHz or 2.4 GHz to 2.482 GHz, and a pass band of the respective band filters  226   a  to  226   c  may be 2.496 GHz to 2.69 GHz. 
         [0057]    In order to prevent degradation of performance of the short-range wireless communication device due to an RF signal of the detachable wireless access device  230 , a stop band of a band filter (not shown) included in the short-range wireless communication device in the main body unit  210  may be 2.4 GHz to 2.472 GHz or 2.4 GHz to 2.482 GHz. 
         [0058]    When the detachable wireless access device  230  is connected to the main body unit  210 , in order to prevent degradation of performance of the two devices, the host processor  215  of the main body unit  210  may monitor a usage frequency and a reception packet error rate of the short-range wireless communication processor  217  in the main body unit  210  at certain time intervals. If a usage frequency of the short-range wireless communication processor  217  is 2.472 GHz or 2.482 GHz upon monitoring, the host processor  215  may control the detachable wireless access device  230  to make maximum power transmitted from the antenna cradle lower than a certain level, thereby adjusting a reception packet error rate of the short-range wireless communication processor  217  such that it is lower than a certain level. 
         [0059]    If a radio environment of the detachable wireless access device  230  is not good in an area, frequency controlling may be preferentially performed to make the usage frequency of the short-range wireless communication processor lower than  217  2.472 GHz, rather than controlling maximum transmit power of the antenna cradle  220 . 
         [0060]    When the detachable wireless access device  230  is connected to the antenna cradle  220 , an operation of the power amplifier  235  in the detachable wireless access device  230  is changed to a low gain mode in which the power amplifier  235  operates as a pre-amplifier. 
         [0061]    Calibration data such as a gain slop and frequency dependency data with respect to the high output power amplifier  225  of the antenna cradle  220  or temperature dependency data may be stored in a memory (not shown) of the main body unit  210  in the process of mass-production, and may be downloaded to a memory (not shown) of the detachable wireless access device  230  during an initialization process performed after the detachable wireless access device  230  is connected to the antenna cradle  220 . 
         [0062]    The downloaded calibration data may be stored as a separate table different from existing calibration data stored in the memory (not shown) of the detachable wireless access device  230  and may be called to be used only when the detachable wireless access device  230  is connected to the antenna cradle  220  and operates. 
         [0063]    The detachable wireless access device  230  is to perform broadband wireless communication while being carried along, and may have a USB connector  238  for an interface with a computer. When the USB connector  238  is connected with the main body unit  210  via the antenna cradle  220 , it serves as an interface for establishing a communication and control path with the host processor  215 . 
         [0064]    The detachable wireless access device  230  includes an antenna unit  236  including a plurality of transmission/reception antennas for broadband wireless communication, a filter unit  234  including a plurality of band filters to cancel noise from a signal transmitted to or received from the antenna unit  236 , an RF signal processing unit  231  that processes an RF signal transmitted/received via the antenna unit  236 , a broadband communication controller  232  that controls a signal processing operation via the RF signal processing unit  231  and communicates with the main body unit  210  and the antenna cradle  220  to perform a broadband wireless access operation, and a power amplifier that amplifies a signal to be outputted via a transmission antenna of the antenna unit  236 . 
         [0065]    When the detachable wireless access unit  230  is connected to the antenna cradle  220 , a signal path between the antennas  236   a  and the RF signal processing unit  231  in the detachable wireless access device  230  is cut off, and instead, an RF signal path is connected between an antenna provided in the antenna cradle  220  and the RF signal processing unit  231  via an RF connector  236   b.    
         [0066]    The broadband communication controller  232  of the detachable wireless access device  230  may control the high output power amplifier  225  or the antenna switching unit  227  of the antenna cradle  220  via a particular communication port (e.g., a GPIO (General Purpose Input/Output) port), for which the broadband communication controller  232  may have a connector (e.g., a GPIO connector  237 ). In addition, the broadband communication controller  232  may input/output a signal, which is to be processed by the RF signal processing unit  231  via the USB connector  238 , to or from the main body unit  210  or a computer to which the detachable wireless access device  230  is connected. 
         [0067]    The detachable wireless access device  230  may include the power switch  233  to turn on or off power or release a connection to the main body unit  210 . When a connection with the main body unit is released by using the power switch  233 , the indicator unit  211  attached on the front side of the main body unit  210  may indicate an indicator indicating an operation state of the detachable wireless access device  230  as an OFF state. 
         [0068]      FIG. 4  is a view for showing a combination of the broadband wireless access device and a detachable wireless access device according to an embodiment of the present invention. 
         [0069]    As shown in  FIG. 4 , the coupling unit  221  includes the plurality of connection terminals  222  to  224  for forming a communication path when the detachable wireless access device  230  is coupled, and may include the locking unit  229  at one side thereof in order to firmly fix the detachable wireless access device  230 . 
         [0070]    The detachable wireless access device  230  includes the terminals  236  to  238  corresponding to the connection terminals  222  to  224 . The connection terminals of the antenna cradle  220  may be a mail type terminals while the connection terminals of the detachable wireless access device  230  may be female type terminals, but the types of the respective terminals are not limited. 
         [0071]    Here, among the connection terminals, the USB type terminals  224  and  238  are to form a communication path between the main body unit  210  and the detachable wireless access device  230 , the RF signal connection terminals  222  and  236  are to form an RF signal path between the detachable wireless access device  230  and the antenna cradle  220 , and the antenna cradle control terminals  223  and  227  are to form a control path for controlling switching of the antennas provided in the antenna cradle or power amplifier in the detachable wireless access device  230 . 
         [0072]    When the RF signal connection terminals  222  and  236  are connected, the connection between the antenna  236   a  and the RF connector  236   b  provided in the detachable RF connection device  230  is cut off and an RF signal path is formed with the antenna unit  228  provided in the antenna cradle  220 . In this case, the number of RF signal connection terminals  222  and  236  follows the number of transmission paths and reception paths provided in the detachable wireless access device  230 . 
         [0073]    The antenna cradle control terminals  223  and  227  are for switching the antennas provided in the antenna cradle  220 . The USB communication method, according to which the main body unit  210  and the detachable wireless access device  230  are connected, can hardly perform controlling sensitive to timing, so the main body unit does not control the antenna switching but the broadband communication controller  232  controls the antenna switching. 
         [0074]    As the RF signal connection terminals  222  and  236 , RF switch connector elements that are typically applied for mobile terminals may be used. As the antenna cradle control terminals  223  and  227 , a protruded type metal terminal such as a plate spring or a pogo-pin may be used at the cradle side, while only a very small metal terminal that can operate in contact with the terminals of the cradle can be applied to the detachable wireless access device  230  of the counterpart. 
         [0075]    If connections between the RF signal connection terminals  222  and  236  and the antenna cradle control terminals  223  and  227  are unstable, noise would be possibly included, so the locking unit  229  may be provided for a firm fixing. The locking unit  229  may be provided at both sides of the coupling unit  221  or only at an upper side of the coupling unit  221 . For example, the locking unit  229  may employ a lock rob method. 
         [0076]    The above-described positions, shapes and roles of the connection terminals have been described only for explanation and may not be limited thereto. 
         [0077]      FIG. 5  is a view showing a configuration of a connection terminal for connecting the broadband wireless access device and the detachable wireless access device according to an embodiment of the present invention. 
         [0078]    As shown in  FIG. 5 , in order to attach the detachable wireless access device  230  to the antenna cradle  220  or detach the detachable wireless access device  230  from the antenna cradle  220 , the USB connection terminal  224  may be configured to be rotated at a certain angle inwardly or outwardly (or in both forward and backward directions) of the antenna cradle  220  so as to be led in or out (i.e., drawn in or out). In addition, the USB connection terminal  224  as shown in  FIG. 5  has such a structure allowing the detachable wireless access device  230  to be combined at an upper side thereof, but may have a structure allowing the detachable wireless access device  230  to be combined at the side. 
         [0079]    For example, one side of the USB connection terminal  224  of the antenna cradle  220  is rotated outwardly at a certain angle so as to be drawn out to insert the detachable wireless access device  230  therein, and then, the detachable wireless access device  230  inserted in the USB connection terminal  224  is drawn in so as to be combined and then fixed by using the locking units  229 . 
         [0080]    Meanwhile, if the broadband wireless access device and the detachable wireless access device are combined to use a broadband wireless communication frequency and a short-range wireless communication frequency are used, because the two frequency usage bands are close, a mutual frequency interference may occur. Thus, although the filter having the high skirt characteristics as mentioned above is employed to avoid such interference, if the interval between the two frequencies narrows, their mutual interference could not be completely canceled with the filter, and in addition, the degree of mutual interference may vary according to the tolerance of the filter and a temperature change. 
         [0081]    Thus, the present invention further provides a method for complement an interference avoidance by the filter. The frequency interference avoiding method may be performed by using one of the plurality of processors. 
         [0082]    The following description will be based on the assumption that the wireless access device uses both a wireless wide area network (WWAN) including WiMAX and a wireless local area network (WLAN) or personal area network (PAN) including Wi-Fi. In addition, the detachable wireless access device (that can be referred to as ‘broadband wireless communication unit’ or ‘first wireless communication unit’, hereinafter) may perform connection (access) of the WWAN, and the main body unit (referred to as ‘local area wireless communication unit’ or ‘second wireless communication unit’, hereinafter) may perform the local area wireless communication 
         [0083]    The interference avoiding method according to the present invention may be divided into a positive method in which an optimum channel without an interference is searched according to an environment setting or menu selection to avoid an interference and a negative method in which if an interference occurs, local area wireless communication is temporarily paused to avoid interference, and performed. 
         [0084]      FIGS. 6A and 6B  are flow charts illustrating the process of a method for positively avoiding an interference of the broadband wireless access device according to an embodiment of the present invention. 
         [0085]    As shown in  FIGS. 6A and 6B , when power is applied to the broadband wireless access device, the broadband wireless communication unit is initialized (S 101 ) and a channel selection and capability negotiation with a base station is performed (S 102 ). Likewise, the local area wireless communication unit is initialized, and a channel selection and capability negotiation with a base station is performed (S 103 , S 104 ). At this time, the channel is selected by the local area wireless communication unit by giving priority to a lower frequency in order to avoid a frequency interference section. 
         [0086]    When the initialization is completed, each wireless communication unit may monitor a data packet error rate (PER) of a selected channel to check whether the selected channels have mutually interfered with each other. Namely, if the data PER is greater than a particular reference value (minimum spec), it may be determined that the channels mutually interfere with each other, and in this case, a channel having a data PER smaller than the particular reference value should be searched to replace the selected channel. 
         [0087]    The method for searching and changing channels will be described in detail as follows. 
         [0088]    First, if the local area wireless communication unit is not in an idle mode (S 106 ), the data PER is monitored. If the data PER is larger than a first particular reference value (S 107 ), a modulation rate of the local area wireless communication unit is reduced to reduce the data rate (S 108 ). 
         [0089]    And then, it is checked whether the data rate of the broadband wireless communication unit is larger than or the same as that of the local area wireless communication unit in the current channel, and also it is checked whether the current channel satisfies the QoS policy of the data of the broadband wireless communication unit (S 109 ). If the two conditions are all met in step S 109 , steps S 105  to S 109  are repeatedly performed, and any one of the conditions is not met, the step S 110  is performed. 
         [0090]    The transmit power of the broadband wireless communication unit is gradually reduced stepwise, and then, it is checked whether the current channel satisfies the data QoS policy of the broadband wireless communication (S 111 ). If the current channel satisfies the data QoS policy of the broadband wireless communication unit, steps S 105  to S 109  are repeatedly performed. 
         [0091]    If the current channel does not satisfy the data QoS policy of the broadband wireless communication unit in step S 111 , step S 126  is performed. Namely, because the local area wireless communication unit cannot be used until before a communication environment is changed as a particular event occurs, it is monitored as to whether a particular event occurs (S 126 ). 
         [0092]    The particular event includes an event that the broadband wireless communication unit performs handover or that transmit power is controlled (S 115 ), an event that a channel of the WLAN is changed or transmit power is controlled (S 116 ), or a periodical interrupt check event by a watch dog timer (S 117 ). 
         [0093]    If the data PER of the local area wireless communication unit is smaller than the first particular reference value in S 107 , a PER of the broadband wireless communication unit is monitored in S 112 . It is checked whether the PER of the broadband wireless communication unit is lower than a second particular reference value in S 113 . 
         [0094]    If the PER of the broadband wireless communication unit is smaller than the second particular reference value, the broadband wireless communication unit and the local area wireless communication unit normally operate without a mutual interference until before the particular event occurs in S 114 . 
         [0095]    The method for searching a channel by the local area wireless communication unit if the data PER of the broadband wireless communication unit is not smaller than the second particular reference value in S 113  will now be described. 
         [0096]    In this case, channel searching may be immediately performed if the local area wireless communication unit is in an idle mode, and whether or not the local area wireless communication is in the idle mode is determined in step S 106 . 
         [0097]    If a local area wireless communication channel is searched in S 118 , it is checked whether the searched channel is a valid channel in S 119 . If the searched channel is a valid channel, the current local area wireless communication channel is changed to the searched valid channel and a capability negotiation with respect to the changed channel is performed. And then, steps S 112  and S 113  are performed. Steps S 118  to S 120  may be repeatedly performed according to determinations at the step S 113 . 
         [0098]    If there is no valid channel in the searched channels in S 118 , the transmit power of the local area wireless communication unit is reduced in S 121 , and a PER of the broadband wireless communication unit is monitored in S 122 . It is checked whether the data PER of the broadband wireless communication unit is smaller than the second particular reference value in S 123 . If the data PER of the broadband wireless communication unit is smaller than the second particular reference value, step S 124  is performed. Namely, the broadband wireless communication unit and the local area wireless communication unit normally operate without a mutual interference until before a particular event occurs. 
         [0099]    It is checked whether the data rate of the broadband wireless communication unit is larger than or the same as that of the local area wireless communication unit in the current channel, and also it is checked whether the current channel satisfies the QoS policy of the data of the broadband wireless communication unit (S 125 ). If the two conditions are all met in step S 125 , steps S 121  to S 125  are repeatedly performed, and any one of the conditions is not met, the step S 126  is performed. Namely, because the local area wireless communication unit cannot be used until before a communication environment is changed as a particular event occurs, it is monitored as to whether a particular event occurs (S 126 ). 
         [0100]      FIGS. 7A and 7B  are flow charts illustrating the process of a method for negatively avoiding an interference of the broadband wireless access device according to an embodiment of the present invention. 
         [0101]    As shown in  FIGS. 7A and 7B , when power is applied to the broadband wireless access device, the broadband wireless communication unit is initialized (S 201 ), selects a channel selection and performs a capability negotiation with the base station (S 202 ). Likewise, the local area communication unit is initialized, selects a channel and performs a capability negotiation (S 203 , S 204 ). In this case, the channel selected by the local area wireless communication unit is selected by giving priority to channel having a lower frequency to avoid a frequency interference section. 
         [0102]    After the initialization is completed, if the local area wireless communication unit is not in an idle mode (S 206 ), a data PER is monitored (S 206 ). If the data PER is larger than a first particular reference value (s 207 ), the local area wireless communication unit cannot be used until before a particular event occurs and a communication environment is changed (S 217 ). 
         [0103]    If the data PER of the local area wireless communication unit is smaller than the first particular reference value, a local area wireless communication channel for which the data PER of the broadband wireless communication unit is smaller than the second particular reference value is searched to change the current channel (S 208  to S 210 ). Namely, the data PER of the broadband wireless communication unit is monitored (S 208 ). If the data PER is larger than the second particular reference value (S 209 ), a valid channel that is not used by other terminals among a plurality of local area wireless communication channels is searched to replace the current channel (S 214  to S 216 ). If there is no valid channel in channel searching (S 215 ), the local area wireless communication unit cannot be used until before a particular event occurs and the communication environment is changed (S 217 ). 
         [0104]    The channel searching can be immediately performed if the local area wireless communication unit is in the idle mode (S 206 ). In addition, a channel having a low frequency is preferentially searched, and when the current channel is changed by the searched channel, a capability negotiation is performed on the searched channel (S 216 ). 
         [0105]    If a channel of the local area wireless communication unit for which the data PER of the broadband wireless communication unit is smaller than the second particular reference value is searched to replace the current channel, the broadband wireless communication unit and the local area communication unit can normally operate without a mutual interference until before a particular event occurs (S 210 ). 
         [0106]    As the exemplary embodiments may be implemented in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its scope as defined in the appended claims. Therefore, various changes and modifications that fall within the scope of the claims, or equivalents of such scope are therefore intended to be embraced by the appended claims.