Patent Publication Number: US-2010128670-A1

Title: Base station interference-free antenna module and WiFi base station mesh network system using the antenna module

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a base station interference-free antenna module and a wireless fidelity (WiFi) base station mesh network system and, more particularly, to a base station interference-free antenna module capable of improving wireless transmission efficiency of a high frequency signal between two WiFi base stations and the signal to noise ratio (SNR) of wireless transmission of high frequency signals, and the system using the base station interference-free antenna module to effectively reduce the deployment density of WiFi base stations while maintaining the desired quality of service (QoS), in addition to improving the efficiency of wireless transmission of high frequency signals between two WiFi base stations. 
     2. Description of Related Art 
     In recent years, WiFi technology has been widely implemented in the wireless network systems of metropolitan areas, and people can access internet wherever by using a notebook computer or a personal digital assistant (PDA) with wireless capability, thereby gaining the goal of mobile broadband. As shown in  FIG. 1 , a typical WiFi base station mesh network system includes a first WiFi base station  11 , a second WiFi base station  12  and a third WiFi base station  13 . The distances between each two of the base stations range from 50 meters to 150 meters. The first WiFi base station  11  is electrically coupled to a remote server  15  (such as a digital switch) through a physical network line  14 . The second WiFi base station  12  and the third WiFi base station  13  transmit signals received from a client-side electronic device (such as a cell phone, a notebook computer, a PDA and the like) to the first WiFi base station  11  in wireless manner (which is referred to as a cross-link procedure) and subsequently forwards the signals to the remote server  15  through the physical network line  14 . Similarly, the signals are delivered in reverse direction to the first WiFi base station  11  through the physical network line  14  and subsequently transmitted in wireless manner (i.e., the cross-link procedure) to the second WiFi base station  12  or third WiFi base station  13  and finally to the cell phone, the notebook computer or the PDA covered by the second WiFi base station  12  or third WiFi base station  13 . 
     Therefore, the transmission efficiency of signals wirelessly between two WiFi base stations in a typical WiFi base station mesh network system is quite important. In addition, buildings, moving vehicles and dirty air particles in a metropolitan area can cause poor transmission efficiency of the wireless network. Thus, the signal to noise ratio (SNR) of wireless transmission could not be improved effectively, and it is likely resulting in signal loss. In order to maintain a desired QoS, it is necessary to increase the deployment density of WiFi base stations in the typical WiFi base station mesh network system (namely, to reduce the distance between two WiFi base stations). However, it causes that the entire deployment cost of the typical WiFi base station mesh network system is largely increased (for it requires more WiFi base stations), and may also affect on the health of people around the WiFi base stations. 
     To overcome the aforementioned problems, in the industry, a smart antenna is proposed as a solution to replace the wireless transmission antenna of the WiFi base station. The smart antenna can only receive the high frequency signals with a specific frequency, in a specific direction, and within a specific time slot. Accordingly, other high frequency signals with different frequencies or in different directions (such as the high frequency signals reflected by the buildings or transmitted to the WiFi base station by other consumer equipments) are not received by the smart antenna, and the wireless transmission efficiency between the WiFi base stations is improved. However, the smart antenna is very expensive, and the cost could be even higher than the entire WiFi base station. Thus, for the industry, WiFi base stations with the smart antenna could not be implemented widely. Therefore, the smart antenna can only solve partial of the aforementioned problems. 
     Therefore, there is a need for the industry to have a base station interference-free antenna module, which can improve the efficiency and the SNR (signal to noise ration) of wirelessly transmitting high frequency signals between two WiFi base stations, and a WiFi wireless base station mesh network system, which can improve the transmission efficiency of high frequency signals between two WiFi base stations in the system and minimize the deployment density of WiFi base stations in the system under the condition of maintaining a certain level of quality of service (QoS). 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a base station interference-free antenna module, which can increase the wireless transmission efficiency of high frequency signals between two WiFi base stations and also the SNR of wireless transmission of high frequency signals. 
     Another object of the present invention is to provide a WiFi base station mesh network system, which can increase the wireless transmission efficiency of high frequency signals between two WiFi base stations and effectively minimize the deployment density of WiFi base stations while maintaining a desired QoS. 
     To achieve the objects, a base station interference-free antenna module is provided, which is implemented with a signal processor in a wireless fidelity (WiFi) base station and the signal processor is applied to the high frequency signal transmission between the WiFi base station and another WiFi base station. The antenna module includes a plurality of high frequency transceivers facing different directions respectively, and an antenna controller electrically coupled to the high frequency transceivers. The antenna controller is electrically coupled to the signal processor in order to receive a signal transmitting/receiving request output by the signal processor to accordingly select a high frequency transceiver to transmit or receive a circularly polarized high frequency signal. 
     To achieve the objects, a WiFi base station mesh network system is provided. The system includes: a first WiFi base station having a first base station interference-free antenna module and a first signal processor, the base station interference-free antenna module having a plurality of first high frequency transceivers facing different directions respectively, and a first antenna controller electrically coupled to the first high frequency transceivers respectively. The first antenna controller is electrically coupled to the first signal processor in order to select a first high frequency transceiver based on a signal transmitting/receiving request output by the first signal processor to thereby transmit or receive a circularly polarized first high frequency signal; and a second WiFi base station having a second base station interference-free antenna module and a second signal processor, the second base station interference-free antenna module having a plurality of second high frequency transceivers facing different directions respectively, and a second antenna controller electrically coupled to the second high frequency transceivers respectively. The second antenna controller is electrically coupled to the second signal processor to select a second high frequency transceiver based on a signal transmitting/receiving request output by the second signal processor to thereby transmit or receive a circularly polarized second high frequency signal. In addition, one of the first high frequency transceivers faces the second WiFi base station, and one of the second high frequency transceivers faces the first WiFi base station. 
     Therefore, the high frequency signals transmitted by the high frequency transceivers of the base station interference-free antenna module in the invention have a circular polarization characteristic (such as left-hand circular polarization), and when the circularly polarized high frequency signals are reflected by an obstacle (such as a building or vehicle), its circular polarization characteristic would be changed (such as changed from left-hand circular polarization to right-hand circular polarization). Therefore, the antenna controller of the base station interference-free antenna module of a second WiFi base station can deliver only the high frequency signal with a specific circular polarization (such as left-hand circular polarization) to the signal processor by the internal circular polarization filtering property. In this case, even if the reflected high frequency signals are received by the second high frequency transceivers of the second WiFi base station, they cannot enter the signal processor due to the right-hand circular polarization characteristic. Namely, the noises produced by the reflected high frequency signal or signals are effectively suppressed, so the SNR of wirelessly transmitting the high frequency signals can be raised and the wireless transmission efficiency of high frequency signals between two WiFi base stations is raised. 
     Similarly, since each high frequency transceiver of the antenna module respectively in the two WiFi base stations of the WiFi base station mesh network system can transmit or receive circularly polarized high frequency signals, the other WiFi base station can easily receive the high frequency signal with the same circular polarization when one WiFi base station transmits the high frequency signal with a specific circular polarization, and the SNR and the transmission efficiency are accordingly raised when wirelessly transmitting the high frequency signals. Therefore, the WiFi base station mesh network system can increase the distance between the WiFi base stations (i.e., reduce the deployment density of the WiFi base stations), while maintaining the desired QoS. 
     Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a typical WiFi base station mesh network system; 
         FIG. 2  is a schematic view of a base station interference-free antenna module according to an embodiment of the invention; 
         FIG. 3  is a schematic view of a WiFi base station mesh network system according to an embodiment of the invention; 
         FIG. 4  is a schematic view of a first WiFi base station of a WiFi base station mesh network system according to an embodiment of the invention; and 
         FIG. 5  is a schematic view of a second WiFi base station of a WiFi base station mesh network system according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 2  is a schematic view of a base station interference-free antenna module according to an embodiment of the invention. As shown in  FIG. 2 , the module includes a plurality of high frequency transceivers  21  to  26  and an antenna controller  27 . The high frequency transceivers  21  to  26  face different directions respectively, and the antenna controller  27  is electrically coupled to the high frequency transceivers  21  to  26  respectively. In addition, the base station interference-free antenna module is implemented in a wireless fidelity (WiFi) base station (shown later) and applied to a high frequency signal transmission between the WiFi base station and another WiFi base station (shown later). 
     The WiFi base station (shown later) with the base station interference-free antenna module has a signal processor (shown later), and the antenna controller  27  is electrically coupled to the signal processor (shown later). The antenna controller  27  is based on a signal transmitting/receiving request output by the signal processor to select one of the high frequency transceivers  21 ,  22 ,  23 ,  24 ,  25  and  26  to transmit or receive the circularly polarized high frequency signal. 
     The antenna module shown in  FIG. 2  has one to six high frequency transceivers  21  to  26 , each being a patch array antenna, and each of the high frequency transceivers  21  to  26  has a rectangle plate  211 ,  221 ,  231 ,  241 ,  251 ,  261 . In this embodiment, the rectangle plates  211 ,  221 ,  231 ,  241 ,  251 ,  261  have a size of 10 cm×10 cm. The antenna controller  27  includes a circular polarization filter portion  271  to filter the high frequency signals respectively received by the high frequency transceivers  21  to  26 . Thus, only the high frequency signal with a specific circular polarization (such as left-hand circular polarization) can be obtained and delivered to the signal processor (shown later) of the WiFi base station (shown later). 
     In this embodiment, the antenna controller  27  includes an electronic scan switch circuit board  272  to rapidly switch and select one of the high frequency transceivers  21 ,  22 ,  23 ,  24 ,  25  and  26  electronically based on the signal transmitting/receiving request output by the signal processor to thereby transmit or receive a circularly polarized high frequency signal. In this embodiment, the frequency of the circularly polarized high frequency signals transmitted or received by the high frequency transceivers  21 ,  22 ,  23 ,  24 ,  25  and  26  is about 2.4 GHz (upon the practical needs, the actual frequency is slightly varied in a frequency range between 3.4 GHz and 3.6 GHz or between 5.6 GHz to 5.8 GHz, for example). 
     It is noted that the number of high frequency transceivers of the base station interference-free antenna module can be one to six, depending on the practical needs, but not limited to six as cited in this embodiment. In addition, depending on the practical needs, each of the high frequency transceivers can be a different type of antenna, which is capable of transmitting or receiving circularly polarized high frequency signals, such as a waveguide slot array antenna or a sector horn antenna, but not limited to the patch array antenna as cited in this embodiment, and all the high frequency transceivers do not need to be the same type of antenna. The high frequency signal can range between 2.3 GHz and 2.5 GHz, between 3.4 GHz and 3.6 GHz or between 5.6 GHz and 5.8 GHz, depending on the practical needs (such as in different environments), but not limited to 2.4 GHz as cited in this embodiment. 
     Since the circular polarization characteristic of the high frequency signals is changed when the high frequency signals are reflected by obstacles, the circular polarization characteristic can be restored to the original circular polarization (such as the left-hand circular polarization) when the high frequency signals are reflected again. In this case, although the circularly polarized high frequency signals which have been reflected twice could pass the circular polarization filter portion of the antenna controller of the base station interference-free antenna module of the second WiFi base station and be delivered to the signal processor of the second WiFi base station, the strength of the high frequency signals is decayed to a very low level after being reflected twice, and the wireless transmission of high frequency signals between the WiFi base stations would not be affected by the noises produced by the high frequency signals which have been reflected twice. Namely, for the base station interference-free antenna module in this embodiment, the SNR of wirelessly transmitting the high frequency signals is not decreased due to the high frequency signals which have been reflected twice. Therefore, the wireless transmission efficiency of high frequency signals between two WiFi base stations is raised by using the base station interference-free antenna module. 
       FIG. 3  is a schematic view of a WiFi base station mesh network system according to an embodiment of the invention. As shown in  FIG. 3 , the WiFi base station mesh network system includes a first WiFi base station  3  and a second WiFi base station  4 . The distance between the WiFi base stations  3  and  4  ranges between 200 meters and 300 meters, which is far greater than that in a typical base station mesh network system (which is about between 50 meters and 150 meters). 
       FIG. 4  is a schematic view of the first WiFi base station  3  according to an embodiment of the invention. As shown in  FIG. 4 , the first WiFi base station  3  includes a first base station interference-free antenna module  31  and a first signal processor  32 . The first base station interference-free antenna module  31  has a plurality of first high frequency transceivers  311  to  316  and a first antenna controller  317 . The first high frequency transceivers  311  to  316  face different directions respectively. The first antenna controller  317  is electrically coupled to the high frequency transceivers  311  to  316  respectively. In addition, the first antenna controller  317  is electrically coupled to the first signal processor  32  in order to select one of the first high frequency transceivers  311 ,  312 ,  313 ,  314 ,  315  and  316  based on a signal transmitting/receiving request output by the first signal processor  32  to thereby transmit or receive the circularly polarized first high frequency signal. As shown in  FIG. 3 , the first WiFi base station  3  is electrically coupled to a remote server  34  through a physical network line  33 . In this embodiment, the physical network line  33  could be a network cable of a backbone network, and the remote server is a server located in a switch room. 
       FIG. 5  is a schematic view of the second WiFi base station  4  according to an embodiment of the invention. As shown in  FIG. 5 , the second WiFi base station  4  includes a second base station interference-free antenna module  41  and a second signal processor  42 . The second base station interference-free antenna module  41  has a plurality of second high frequency transceivers  411  to  416  and a second antenna controller  417 . The second high frequency transceivers  411  to  416  face different directions respectively. The second antenna controller  417  is electrically coupled to the second high frequency transceivers  411  to  416  respectively. In addition, the second antenna controller  417  is electrically coupled to the second signal processor  42  in order to select one of the second high frequency transceivers  411 ,  412 ,  413 ,  414 ,  415  and  416  based on a signal transmitting/receiving request output by the second signal processor  42  to thereby transmit or receive a circularly polarized second high frequency signal. 
     As shown in  FIG. 3 , one of the first high frequency transceivers  311  to  316  (in this case, the first high frequency transceiver  311 ) faces the second WiFi base station  4 , and one of the second high frequency transceivers  411  to  416  (in this case, the second high frequency transceiver  411 ) faces the first WiFi base station  3 . 
     In this embodiment, the first base station interference-free antenna module  31  shown in  FIG. 4  has six first high frequency transceivers  311  to  316 , each being a patch array antenna. Each of the first high frequency transceivers  311  to  316  has a rectangle plate  3111 ,  3121 ,  3131 ,  3141 ,  3151 ,  3161 , with a size of 10 cm×10 cm. The first antenna controller  317  includes a circular polarization filter portion  3171  to filter the first high frequency signals respectively received by the first high frequency transceivers  311  to  316 . Thus, only the first high frequency signal with a specific circular polarization (such as left-hand circular polarization) can be obtained and delivered to the first signal processor  32  of the first WiFi base station  3 . In addition, in this embodiment, the first antenna controller  317  includes an electronic scan switch circuit board  3172  to rapidly switch and select one of the first high frequency transceivers  311 ,  312 ,  313 ,  314 ,  315  and  316  electronically based on a signal transmitting/receiving request output by the first signal processor  32  to thereby transmit or receive a circularly polarized first high frequency signal. In this case, the frequency of the circularly polarized first high frequency signals transmitted or received by the first high frequency transceivers  311 ,  312 ,  313 ,  314 ,  315  and  316  is about 2.4 GHz (upon the practical needs, the actual frequency is slightly varied in a frequency range between 3.4 GHz and 3.6 GHz or between 5.6 GHz to 5.8 GHz, for example.) 
     As shown in  FIG. 5  again, in this embodiment, the second base station interference-free antenna module  41  has six second high frequency transceivers  411  to  416 , each being a waveguide slot array antenna and has a rectangle plate  4111 ,  4121 ,  4131 ,  4141 ,  4151 ,  4161  respectively, with a size of 10 cm×10 cm. The second antenna controller  417  includes a circular polarization filter portion  4171  to filter the second high frequency signals respectively received by the second high frequency transceivers  411  to  416 . Thus, only a second high frequency signal with a specific circular polarization (such as a left-hand circular polarization) can be delivered to the second signal processor  42  of the second WiFi base station  4 . 
     In addition, in this embodiment, the second antenna controller  417  includes an electronic scan switch circuit board  4172  to rapidly switch and select one of the high frequency transceivers  411 ,  412 ,  413 ,  414 ,  415  and  416  electronically based on a signal transmitting/receiving request output by the first signal processor  42  to thereby transmit or receive a circularly polarized second high frequency signal. In this embodiment, the frequency of the circularly polarized second high frequency signals transmitted or received by the second high frequency transceivers  411 ,  412 ,  413 ,  414 ,  415  and  416  is about 2.4 GHz (upon the practical needs, the actual frequency is slightly varied in a frequency range between 3.4 GHz and 3.6 GHz or between 5.6 GHz to 5.8 GHz, for example.) 
     As shown in  FIG. 3 , when the first WiFi base station  3  receives a signal to be forwarded to the second WiFi base station  4  through the physical network line  33 , it converts the signal into a corresponding circularly polarized first high frequency signal. Next, the first antenna controller  317  of the first WiFi base station  3  selects the first high frequency transceiver  311  facing the second WiFi base station  4  to transmit the first high frequency signal, and the second antenna controller  417  of the second WiFi base station  4  thus selects the second high frequency transceiver  411  facing the first WiFi base station  3  to receive the first high frequency signal. 
     In addition, when the second WiFi base station  4  wants to deliver a signal output by the client-side electronic device to the remote server  34 , the second antenna controller  417  of the second WiFi base station  4  selects the second high frequency transceiver  411  facing the first WiFi base station  3  to transmit a corresponding circularly polarized second high frequency signal. In this case, the first antenna controller  317  of the first WiFi base station  3  thus selects the first high frequency transceiver  311  facing the second WiFi base station  4  to receive the second high frequency signal. Next, the first WiFi base station  3  converts the received second high frequency signal into a circuit signal and forwards the circuit signal to the remote server  34  through the physical network line  33 . 
     It is noted that, depending on the practical needs, the number of first high frequency transceivers of the first base station interference-free antenna module and the number of second high frequency transceivers of the second station interference-free antenna module can be one to six, but not limited to six as cited in this embodiment. In addition, depending on the practical needs, each of the first high frequency transceivers can be a different type of antenna, which is capable of transmitting or receiving a circularly polarized high frequency signal, such as a waveguide slot array antenna or a sector horn antenna, but not limited to the patch array antenna as cited in this embodiment, and all of the first high frequency transceivers do not need to be the same type of antenna. 
     Similarly, depending on the practical needs, each of the second high frequency transceivers can be a different type of antenna, which is capable of transmitting or receiving a circularly polarized high frequency signal, such as a patch array antenna or a sector horn antenna, not limited to a waveguide slot array antenna as cited in this embodiment, and all the second high frequency transceivers do not need to be the same type of antenna. The frequency of the first and the second high frequency signals can range between 2.3 GHz and 2.5 GHz, between 3.4 GHz and 3.6 GHz or between 5.6 GHz and 5.8 GHz, depending on the practical needs (such as in different environments), not limited to 2.4 GHz as cited in this embodiment. 
     As stated, the WiFi base station  3  of the WiFi base station mesh network system of the other embodiment of this invention, uses the first frequency transceiver  311  of the first base station interference-free antenna module  31  to transmit the first high frequency signal, which has a circular polarization characteristic (such as left-hand circular polarization). After the first high frequency signal is reflected by an obstacle (such as a building or vehicle), its circular polarization characteristic would be changed (such as from left-hand circular polarization to right-hand circular polarization). At this point, as the circular polarization filter portion  4171  of the second antenna controller  417  of the second WiFi base station  4  limits that only a first high frequency signal with a specific circular polarization (such as a left-hand circular polarization) can pass and be delivered to the second signal processor  42 , the first high frequency signals reflected by the obstacle cannot be delivered to the second signal processor  42  of the second WiFi base station  4  even they enter the high frequency transceivers  411  to  416  of the second WiFi base station  4 . Accordingly, the noises produced by the reflected first high frequency signals are effectively suppressed, and the SNR of wirelessly transmitting the first high frequency signals is raised. 
     Since the circular polarization characteristic of the high frequency signals would be changed after the signals are reflected by the obstacle, the circular polarization characteristic can be restored to the original circular polarization (such as the left-hand circular polarization) when the first high frequency signals are reflected again. In this case, even though the circularly polarized first high frequency signals which have been reflected twice is able to pass the circular polarization filter portion  4171  of the antenna controller  417  of the antenna module  41  of the second WiFi base station  4 , and be delivered to the signal processor  42 , the strength of the first high frequency signals is decayed to a very low level after being reflected twice, and the wireless transmission of the first high frequency signal between two WiFi base stations (in this case, the first and the second WiFi base station  3  and  4 ) would not be affected by the noises produced by the first high frequency signals which have been reflected twice. Accordingly, the SNR of wirelessly transmitting the first high frequency signals would not be decreased by the first high frequency signals which have been reflected twice, and in the WiFi base station mesh network system, the wireless transmission efficiency of the first high frequency signal between two WiFi base stations (in this case, the first and the second WiFi base station  3  and  4 ) is raised. 
     Since the wireless transmission efficiency of the first high frequency signal between two WiFi base stations (in this case, the first and the second WiFi base station  3  and  4 ) and the SNR of the wireless transmission are raised, the distance between the WiFi base stations in the WiFi base station mesh network system can be increased (i.e., the deployment density of the WiFi base stations is reduced), but the QoS (such as signal stability and signal loss ratio) is maintained at a desired level. 
     To summarize, the high frequency signals transmitted by the high frequency transceivers of the base station interference-free antenna module have a circular polarization (such as left-hand circular polarization) characteristic, and the circular polarization characteristic would be changed (such as from left-hand circular polarization to right-hand circular polarization) when the high frequency signals are reflected by an obstacle (such as a building or vehicle). Thus, as the circular polarization filtering property of the antenna controller of the base station interference-free antenna module of the other WiFi base station limits that only a high frequency signal with a specific circular polarization (such as left-hand circular polarization) can pass and be delivered to the signal processor, the high frequency signals reflected by the obstacle cannot be delivered to the signal processor of the other WiFi base station because of its right-hand circular polarization, even if they enter the high frequency transceivers of the other WiFi base station. Accordingly, the noises produced by the reflected high frequency signals are effectively suppressed and thereby the SNR of wirelessly transmitting the high frequency signals is raised, and the wireless transmission efficiency of the high frequency signals between two WiFi base stations is also raised. 
     Similarly, since all of the high frequency transceivers of the antenna module of the WiFi base stations in the WiFi base station mesh network system can transmit or receive a circularly polarized high frequency signal, the other WiFi base station can easily receive the circularly polarized high frequency signal when one of the WiFi base stations transmits the circularly polarized high frequency signal, and the SNR and the transmission efficiency of wirelessly transmitting the high frequency signals are accordingly raised. Thus, the distance between the WiFi base stations in the WiFi base station mesh network system can be increased (i.e., the deployment density of the WiFi base stations can be decreased) while maintaining the QoS at a certain level. 
     Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.