Patent Publication Number: US-2007110097-A1

Title: Wireless communication system, communication method and computer readable medium thereof

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
      This application claims priority to Taiwan Patent Application No. 094140349 filed on Nov. 16, 2005.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a wireless communication system, a communication method and a computer readable medium thereof. More specifically, it relates to a wireless communication system, a communication method, and a computer readable medium thereof communicating by using an inactive period when a regular communication is interfered.  
      2. Descriptions of the Related Art  
      Wireless network is one of necessary communication media in the future. However, noise interferences are frequently occurred in data transmission because it is very easy to have other signals in the same operation environment. This problem not only slows down the transmitting speed, but also results in communication interruptions. Therefore, it is necessary to develop a stable communication for wireless network with interference-free capability so as to enhance the communication quality of the wireless network.  
      In the conventional wireless communication system, it is common to use an additional device so as to reduce the effects from an interference source. As shown in  FIG. 1 , the conventional wireless communication system comprises a selection and distribution device  11 , a terminal device  15 , and a beacon signal generator  13 . The beacon signal generator  13  is adjacently disposed to the selection and distribution device  11 , and signals from both devices are under the same signal coverage  17 . The beacon signal generator  13  regularly transmits a beacon signal  10  which carries channel usage information. The selection and distribution device  11  switches to another communication channel if the selection and distribution device  11  is affected by an interference source  19 . The terminal device  15  then switches to the new channel which is used by the selection and distribution device  11  after acquiring the information from the beacon signal  10 . Said system requires additional hardware devices (beacon signal generator  13 ) to be able to operate and merely gives consideration for the communicating situation of the selection and distribution device  11  but the terminal device which is interfered. Therefore, in the prior art, additional elements and extra costs are required. Moreover, the prior art is inapplicable if only the terminal device  15  is interfered.  
      There are other conventional methods available such as regularly switching channels for the wireless communication system so as to avoid communication interference. Such method does not have to replace conventional hardware dispositions. Every channel used by all of the devices could be selected and controlled simply by controlling software so as to set channel parameters, which are used to regularly switch channels in the wireless communication system. However, such method cannot ensure that all of the devices are interference-free even after the switch of the channels. Besides, all of the devices have to regularly switch channels no matter whether there is any interference in the system. Such operation would reduce the efficiency of the whole network and increase energy dissipation when there is no interference source in the system.  
      According to the above descriptions, the current wireless communication systems and method for reducing interference effects have problems in higher costs, worse application, and more system energy dissipations, etc. Therefore, a wireless communication system and method without extra hardware devices, saving energy resources, adjusting channels appropriately, and being able to be widely applied in a variety of interfered situations, which is desirable in this field.  
     SUMMARY OF THE INVENTION  
      The primary object of the present invention is to provide a wireless communication system. The wireless communication system communicates via a beacon. The beacon defines an active period and an inactive period. The wireless communication system comprises a terminal device, and a selection and distribution device for initially using a first channel in the active period to communicate with each other. The selection and distribution device communicates with the terminal device by using a second channel in the inactive period when the first channel is interfered.  
      Another object of the present invention is to provide a selection and distribution device for the wireless communication system described above. The selection and distribution device communicates with a terminal device via a beacon and initially uses a first channel in the active period to communicate with the terminal device. The selection and distribution device communicates with the terminal device by using a second channel in the inactive period when the first channel is interfered.  
      Yet a further object of the present invention is to provide a terminal device for the wireless communication system described above. The terminal device communicates with a selection and distribution device via a beacon and initially uses a first channel in the active period to communicate with the selection and distribution device. The terminal device sends an SOS signal when the first channel is interfered and the terminal device communicates with the selection and distribution device by using a second channel in the inactive period in response to the SOS signal.  
      Still a further object of the present invention is to provide a communication method for a wireless communication system. The wireless communication system communicates via a beacon and comprises the steps of: using a first channel in the active period to communicate; determining whether the first channel is interfered; and if so, using a second channel in the inactive period to communicate.  
      Another object of the present invention is to provide a computer readable medium which stores a computer program to perform said communication method.  
      The detailed technology and preferred embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic diagram illustrating a conventional wireless communication system using an extra device to reduce effects from an interference source;  
       FIG. 2  is a schematic diagram of the first embodiment of the present invention;  
       FIG. 3  is a schematic diagram of a beacon;  
       FIG. 4  is a schematic diagram of the second embodiment of the present invention;  
       FIG. 5  is a flow chart of the third embodiment of the present invention; and  
       FIG. 6  is a flow chart of the fourth embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
      A wireless communication system  2  in the first embodiment of the present invention is shown in  FIG. 2 . The wireless communication system  2  comprises a terminal device  21  and a selection and distribution device  23  that communicate with each other via a beacon. An interference source  25  also exists in the wireless communication environment  27  of the wireless communication system  2 . A general beacon is illustrated in  FIG. 3 . A beacon  3  comprises an active period  31  and an inactive period  33 . The active period  31  is for transmitting data and the inactive period  33  is a suspension period for data transmission. In other words, the inactive period  33  is not used for data transmission. The selection and distribution device  23  initially uses a first channel in the active period to communicate with the terminal device  21 . When the interference source  25  interferes with one of the terminal device  21  and the selection and distribution device  23 , the selection and distribution device  23  would determine whether the continuing use of the first channel will be interfered. Therefore, the selection and distribution device  23  will use a second channel in the inactive period  33  to communicate with the terminal device  21  wherein the second channel could be any available channel for the wireless communication system  2  other than the first channel. In this embodiment, the selection and distribution device  23  could be a router or a coordinator.  
      More particularly, the selection and distribution device  23  and the terminal device  21  use the first channel to transmit data when the selection and distribution device  23  using the first channel to communicate with the terminal device  21  without any interference from the interference source  25 . However, if the communication is interfered, the selection and distribution device  23  and the terminal device  21  further use the second channel in the inactive period  33  to transmit same date in addition to the first channel in the active period  31 . The communication could be maintained because the second channel is not interfered by the interference source  25 .  
      When the selection and distribution device  23  uses the second channel in the inactive period  33  to communicate with the terminal device  21  and if the terminal device  21  responds availability for using the second channel to communicate, the selection and distribution device  23  could choose continuingly using both the first channel in the active period  31  and the second channel in the inactive period  33  to communicate, or only using the second channel in the active period  31  to communicate while the inactive period  33  restores to not transmitting data.  
      In this embodiment, the selection and distribution device  23  determines whether the use of the first channel will be interfered, including by receiving an SOS signal from the terminal device. More specifically, the terminal device  21  evaluates the channel quality when the selection and distribution device  23  merely uses the first channel to communicate with the terminal device  21  initially. If the channel quality is inferior, the terminal device  21  sends an SOS signal to the selection and distribution device  23 . When the selection and distribution device  23  receives the SOS signal, the interference in the first channel will be confirmed and the second channel in the inactive period could be used to communicate.  
      In this embodiment, the selection and distribution device  23  determines whether the use of the first channel to communicate is interfered, further including by the failure in communicating with the terminal device  21  via the first channel for N times. In a normal communication, the terminal device  21  sends a determining signal to the selection and distribution device  23  after receiving a beacon  3 . When the first channel is interfered, the selection and distribution device  23  could not receive the determining signal. The selection and distribution device  23  determines that the first channel is interfered after the failure of in receiving the determining signal for N times. Then, the second channel in the inactive period is used to communicate. Likewise, when the first channel is interfered, the terminal device  21  tries to communicate for N times. If the beacon  3  can not be received for N times, the terminal device  21  sends an SOS signal to the selection and distribution device  23  informing that the first channel is interfered. Time for waiting to receive the beacon  3  is extended and trial times is reset, so as to continue trying to receive the beacon  3  if the beacon  3  is still not received after the terminal device sent the SOS signal. N is predetermined in the above descriptions.  
      The second embodiment, a wireless communication system as well, of the present invention is shown in  FIG. 4 . The difference to the first embodiment is that a wireless communication system  4  comprises five terminal devices and four selection and distribution devices wherein five terminal devices are a first terminal device  401 , a second terminal device  403 , a third terminal device  405 , a fourth terminal device  407 , and a fifth terminal device  409 ; four selection and distribution devices are a coordinator  411 , a first router  413 , a second router  415  and a third router  417 . The wireless communication system  4  communicates via a beacon as well. The beacon also defines an active period and an inactive period. The coordinator  411 , first router  413 , second router  415 , third router  417 , and the first, second, third, and fourth terminal devices  401 ,  403 ,  405 , and  407  initially communicate via a first channel in the active period. The communication in the first router  413 , second router  415  and the third terminal device  405  under the interference source effect coverage  419 , would be affected when they are affected by an interference source (not shown in the figure). Not only the first router  413 , and second router  415  respectively communicate with the third terminal device  405  via the second channel in the inactive period, but also the coordinator  411  communicates with the first router  413  and the second router  415  communicates with the third router  417  via the second channel in the inactive period. The first terminal device  401 , second terminal device  403 , fourth terminal device  407  and fifth terminal device  409  that are not affected by the interference source still merely communicate via the first channel in the active period.  
      For example, the coordinator  411  needs to transmit data to the fourth terminal device  407 , then the coordinator  411  transmits the data to the first router  413  via the first channel in the active period and also via the second channel in the inactive period. The first router  413  transmits the data to the second router  415  via the first channel in the active period and also via the second channel in the inactive period. The second router  415  transmits the data to the third router  417  via the first channel in the active period and also via the second channel in the inactive period. The third router  417  transmits the data to the fourth terminal device  407  via the first channel in the active period.  
      The third embodiment of the present invention is a communication method for a wireless communication system, as shown in  FIG. 5 . The wireless communication system communicates via a beacon. The beacon defines an active period and an inactive period. When step  500  is performing, it communicates via a first channel in the active period. Afterwards, step  501  is performed for determining whether the communication is affected by using the first channel. If so, it indicates that other channels are needed for the system to communicate. Thus, step  502  is performed for using a second channel in the inactive period to communicate. If not, it indicates that the first channel is useable for communication. Thus, the communication method goes back to step  500 , and communicates via the first channel in the active period. After waiting a predetermined period of time, the communication method continues to perform step  501  for determining whether the communication is affected by using the first channel.  
      The communication method further determines whether an SOS signal is received when performing step  501 . If so, it indicates that the first channel is interfered, then performs step  502 . The step  501  could also determine whether it fails in communicating via the first channel for N times. If so, it indicates that the first channel is interfered.  
      The fourth embodiment of the present invention is another communication method, as shown in  FIG. 6 . When step  600  is performing, it communicates via a first channel in an active period. Afterwards, step  601  is performed for determining whether the communication is affected by using the first channel. If so, performs step  602  for using another channel, such as a second channel, in the inactive period to communicate. It is different from the third embodiment that when step  603  is performed after step  602 , it determines whether receives a response for availability of the second channel. If so, it indicates that the second channel is available for communication without influence from an interference source. Then, step  604  is performed for alternatively communicating via the second channel in the active period and data transmission in the inactive period is stopped. If not, it indicates that the second channel is also affected by the interference source. Thus, it goes back to step  602  for communicating via another channel, such as a third channel, in the inactive period. Afterwards, it performs step  603 . If the third channel is still interfered, it chooses another channel, such as a fourth channel, in step  602  until the chosen channel is not interfered.  
      The methods described above could enable the selection and distribution device and/or the terminal device to perform the steps in  FIG. 5  or  FIG. 6  by using a computer readable medium being stored a computer program. The computer readable medium could be floppy disks, hard disks, CD-ROMs, portable storing devices, magnetic tapes, accessible database via network or any other storage media possessing the same functions that people skilled in the art could easily think of.  
      The first, second, third and fourth channels of the present specification merely individually indicate different channels but the number of the channels in the present invention is not limited.  
      Based on the above descriptions, the application of the present invention to the wireless network environment does not need to have extra elements. It could maintain the communication between the selection and distribution device and the terminal device even under interferences. By merely adjusting channels for those interfered devices, it has the advantages of costs reduction, broadly application under different kinds of interferences, and energy saving.  
      The above disclosure is related to the detailed technical contents and inventive features thereof. People skilled in this field may proceed with a variety of modifications and replacements based on the disclosures and suggestions of the invention as described without departing from the characteristics thereof. Nevertheless, although such modifications and replacements are not fully disclosed in the above descriptions, they have substantially been covered in the following claims as appended.