Abstract:
An integrated smart local wireless spread spectrum communication system is disclosed. Smart antennas of the base stations are used to detect the movement of the users. Furthermore, spread spectrum communication technology is used to increase the number of available channels. The signal strength received from the wireless communication unit is used to predict the movement of the communication units, and thus a handoff process can be prepared in advance as the wireless communication unit is in an overlap area between two cells.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a communication system, and more particularly to an integrated smart local wireless spread spectrum communication system.  
           [0003]    2. Description of Prior Art  
           [0004]    Currently, the use of local wireless communication system is restricted by its limited channel numbers, and thus the number of customer is difficult to increase. Moreover, if it is desired to track the movement of a user within the communication system, the transmitting power of the base station must be increased greatly for tracing the local position of the user. Accordingly, the system becomes more complex. Alternatively, a GPS system (global positioning system) can be used for positioning a user. However, it is required to launch several lower orbit satellites, and this will result in a high cost and further requiring purchasing some related software and database. Therefore, the current local wireless communication system still has many defects to be eliminated.  
         SUMMARY OF THE INVENTION  
         [0005]    Accordingly, the primary object of the present invention is to provide an integrated smart local wireless spread spectrum communication system, which employs smart antennas to detect the movement of a user and increase the available channel number so as to increase the number of customers.  
           [0006]    Another object of the present invention is to provide an integrated smart local wireless spread spectrum communication system, which is capable of providing a local positioning function, saving the power consumption of the base station, and reducing the system complexity.  
           [0007]    A further object of the present invention is to provide an integrated smart local wireless spread spectrum communication system, wherein the unlicensed 2.4 GHz band is used so that the cost of communication is low.  
           [0008]    To achieve above object, the integrated smart local wireless spread spectrum communication system in accordance with the present invention includes: at least one mobile wireless communication unit; at least one first base station and one second base station, each providing a cell and having at least one smart antenna array, so that the mobile wireless communication unit in a cell can communicates with a communication device via the base station; and a central control unit for controlling data exchange between the first base station and second base station, and storing user data of the mobile wireless communication unit. In the cell, communication band is divided into a plurality of channels. The first base station and the second base station trace the mobile wireless communication unit by their antennas, respectively, and signal strength of the mobile wireless communication unit received by the antennas are used to determine a moving direction of the mobile wireless communication units. When the mobile wireless communication unit moves from the first base station towards the second base station, the central control unit notifies the second base station, so that the second base station can prepare to perform a handoff process in advance.  
           [0009]    The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a systematic structure of the present invention.  
         [0011]    [0011]FIG. 2 is a flowchart showing the user&#39;s wireless communication cells of the present invention.  
         [0012]    [0012]FIG. 3 is a flowchart of the disconnection process of the present invention.  
         [0013]    [0013]FIG. 4 is a flowchart of the handoff process of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]    In one preferred embodiment of the present invention, a 2.4 GHz system is given as an example in which a mobile phone moves in various base stations. With reference to FIG. 1, there is shown a systematic construction of the present invention, which includes wireless communication units  11  and  12 , base stations  21 ,  22  and  23  and a central control unit  3 .  
         [0015]    In this embodiment, the wireless communication units  11  and  12  are mobile phones. Alternatively, the personal digital assistant (PDA), notebook computer and other personal portable devices may be employed. Each of the base stations  21 ,  22  and  23  provides a wireless coverage, known as a cell. Therefore, a wireless communication unit  11  or  12  can be communicated with the other wireless communication unit  11  or  12  in its cell for transferring voice or data signal. Each of the base stations  21 ,  22  and  23  has a smart antenna array for tracking the movement of the wireless communication unit  11  or  12  in a cell. Furthermore, the communication bandwidth of a cell is divided into a plurality of channels by the spread spectrum technology. Different cells are distinguished by employing different direct sequence spread spectrums (DSSS), so that adjacent cells can use the same channels to perform wireless communications for different wireless communication units  11  and  12 . Between two base stations, for example, base stations  21  and  22 , there is provided an overlap area  4 . The central control unit  3  serves for data exchange among different base stations  21 ,  22  and  23 , and storage of user data. Therefore, a wide area wireless communication environment is constructed.  
         [0016]    [0016]FIG. 2 is a flow diagram illustrating that a user moves in cells. When a user powers on the wireless communication unit  11 , the wireless communication unit  11  registers to the central control unit  3  through the base station  21  (step S 201 ). If the registration is successful, the base station  21  uses its smart antenna to detect the signal strength of the wireless communication unit  11 . If the registration is failed, the central control unit  3  interrupts the communication of the wireless communication unit  11  through the base station  21  (step S 202 ). When the base station  21  detects the signal strength of the wireless communication unit  11 , the signal strength is compared with a predetermined signal strength δ 1 . If the detected signal strength is larger than δ 1 , the detected signal strength is further compared with a predetermined signal strength δ 3 . If the detected signal strength is smaller than δ 1 , the communication of the wireless communication unit  11  is interrupted (step S 202 ). If the detected signal strength of the wireless communication unit  11  is still larger than δ 3 , a connection mode is entered to start a communication (step S 204 ); otherwise, an handoff process is performed for the wireless communication unit  11  (step S 203 ).  
         [0017]    [0017]FIG. 3 shows the flowchart of the interruption process. If a verification is failed (step S 300 ), the base station  21  sends an error message of no system service to the wireless communication unit  11  (step  301 ) and disconnects the connection to the wireless communication unit  11  (step S 303 ′). When the base station  21  detects that the signal strength of the wireless communication unit  11  is smaller than δ 1  (for example, when the user turns off the mobile phone or the user is out of the cell), the base station  21  cancels the registration (step S 302 ), and the connection to the wireless communication unit  11  is disconnected (step S 303 ).  
         [0018]    [0018]FIG. 4 shows the flowchart of the handoff process in accordance with the present invention. When a user having the wireless communication unit  11  moves from a position nearest to the base station  21  towards the base station  22 , and if the smart antenna of the base station  21  detects that the signal strength of the wireless communication unit  11  is smaller than δ 3 , the base station  21  performs a handoff process to the wireless communication unit  11  (step S 401 ). The base station  21  uses the smart antenna to trace the wireless communication unit  11 . Since the smart antenna traces only in one direction and power is transmitted from the base station  21 , the power is greatly reduced, in comparison with that of the conventional multi-direction antenna.  
         [0019]    As the base station  21  keeps tracing the wireless communication unit  11 , the moving direction of the wireless communication unit  11  can be predicted, and thus an adjacent destination base station  22  can be notified of the moving direction (step S 402 ). Therefore, the base station  22  starts to detect the signal strength of the wireless communication unit  11 . At this moment, if the user holding the wireless communication unit  11  moves back to the base station  21 , the base station  21  detects that the signal strength of the wireless communication unit  11  is larger than δ 3 , and thus cancels the handoff process (step S 403 ).  
         [0020]    If the user keeps moving towards the base station  22  and arrives at the overlap area  4  between the base stations  21  and  22 , the base station  21  detects that the signal strength of the wireless communication unit  11  is smaller than δ 2 . Then, the control is switched from the base station  21  to the destination base station  22 , and the corresponding services for the wireless communication unit  11  are then provided by the base station  22 . Moreover, the position of the wireless communication unit  11  is reported to the central control unit  3  (step S 404 ). The base station  22  is responsible for detecting the wireless communication unit  11 . After detecting such, the received signal strength of the wireless communication unit  11  in switching is used as a priority for arranging channels. If the received signal strength is strong, the wireless communication unit  11  has a higher priority. If the base station  21  detects that the signal strength of the wireless communication unit  11  is larger than δ 2 , it represents that the user still moves around in the overlap area  4 . Then, the wireless communication unit  11  is kept in detecting and the detected signal strength is compared with the predetermined signal strengths δ 2  and δ 3 .  
         [0021]    In view of the foregoing, it is appreciated that in the present invention, the movement of the user is detected through smart antennas and the moving direction of the user can be predicted. The smart antenna transmits power toward the detected direction for reducing the loss of power. The base station in the direction is notified of performing a handoff process. Furthermore, a priority process is used for designating a channel to the detected wireless communication unit, thereby improving the quality of service and decreasing the possibility of interruption. Moreover, the spread spectrum technology is used for increasing the number of available communication channels.  
         [0022]    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.