Abstract:
A method for selecting an optimized bandwidth for a geo-location controlled (GDC) station (STA) which does not have location determining capability includes: analyzing first statistical data indicating a bandwidth which is widely deployed across regions; and selecting that bandwidth as the optimized bandwidth. The method further includes checking a configuration file of the GDC STA to determine country information of where the GDC STA was sold; and selecting either a bandwidth corresponding to the country or selecting the bandwidth which is most widely deployed across regions according to the first statistical data as the optimized bandwidth.

Description:
BACKGROUND 
       [0001]    Television channels broadcast signals on Very High Frequency (VHF) and Ultra High Frequency (UHF) bands. In order to prevent interference between adjacent channels within these frequency bands, white spaces are created which are areas where no television signals will be transmitted. On Nov. 4, 2008, the Federal Communications Commission (FCC) of America licensed the use of white spaces for signal transmission by private individuals. The recent switch from analog television to digital has further freed up large amounts of space on the Television White Space (TVWS) spectrum, with the FCC stopping analog transmissions on Jun. 12, 2009. Current regulations in North America allow the use of signals transmitted from portable devices on the frequency band occupied by television channels  21 - 51 , with the proviso that these signals must not interfere with transmissions from television stations and wireless microphones. 
         [0002]    The three main issues confronting the use of the TVWS band for signal transmission are: spatial variation; spectrum fragmentation; and temporal variation. Spatial variation is due to the fact that the availability of channels on the TVWS spectrum depends on location. It cannot be assumed that a particular channel which is free in a first location is also free in a second location. Temporal variation means that a channel may only be free for a limited amount of time. Just as it cannot be assumed that a same channel is free in a first location and a second location, it cannot be assumed that a same channel is free at a first time and a second time. If the channel becomes unavailable, reconfiguration must be performed in order to continue transmissions. Finally, spectrum fragmentation refers to the issue wherein different regulatory bodies use different bandwidths for TVWS band operation. For example, in the United States, Taiwan, South Korea and Japan, individual channels occupy a bandwidth of 6 MHz; in Italy, Australia and New Zealand, individual channels occupy a bandwidth of 7 MHz and in the United Kingdom, France and China, individual channels occupy a bandwidth of 8 MHz. These issues mean that it is necessary to have access to information detailing which channels are currently available, for how long the channels are available, and bandwidth information for the particular region, before signal transmission can begin. 
         [0003]    Many devices which operate on the TVWS band do not have the ability to determine their own location information and therefore cannot select a particular bandwidth for scanning. This means that they must scan on all bandwidths in order to locate access point (AP) beacons. After a first AP beacon is received, the corresponding bandwidth of the beacon is used to determine in which area the GDC dependent STA is located. This method is inefficient and can take up a considerable amount of time and resources. 
       SUMMARY 
       [0004]    It is therefore an objective of the present invention to provide an optimized method for bandwidth selection to increase the probability of finding an AP in a first scan. 
         [0005]    A method for selecting an optimized bandwidth for a geo-location controlled (GDC) station (STA) comprises: analyzing first statistical data to determine a bandwidth; selecting the bandwidth as the optimized bandwidth; and using the optimized bandwidth to communicate with an access point. The GSC STA can be a station that does not have location determining capability. 
         [0006]    The method further comprises: checking a configuration file of the GDC STA to determine country information of where the GDC STA was sold; and selecting either a bandwidth corresponding to the country or selecting the bandwidth which is most widely deployed according to the first statistical data as the optimized bandwidth, wherein when there is no information stored in the configuration file, directly selecting the bandwidth which is most widely deployed according to the first statistical data as the optimized bandwidth. 
         [0007]    The method still further comprises: in a next scanning procedure, selecting the optimized bandwidth as an initial bandwidth for the next scanning procedure, wherein the GDC STA further examines second statistical data of the GDC STA to determine how many consecutive times the initial bandwidth should be scanned, and selecting a different bandwidth from the initial bandwidth according to the statistical data, and the second statistical information comprises information relating to how many times an AP has recently been found on different bandwidths. 
         [0008]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1A  is a flowchart of a method for selecting an optimized bandwidth according to an exemplary embodiment of the present invention. 
           [0010]      FIG. 1B  is a flowchart of a method for selecting a prioritized bandwidth according to an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    The present invention concerns devices which operate on the TVWS band and do not have the ability to determine their own location information. These devices are herein referred to as geo-location dependent controlled (GDC) dependent stations (STA). It is noted that these devices may be portable, i.e. do not have a fixed location, and therefore it cannot be assumed that a previously used bandwidth can be used for a next scanning procedure. Further, as detailed in the background, TVWS has temporal and spatial variation as well as spectrum fragmentation, and therefore each GDC STA must first scan for AP beacons before beginning transmissions in order to confirm which channels on the white spaces are available. 
         [0012]    The present invention therefore provides a number of methods for selecting a scanning bandwidth in a more efficient manner. During a first operation of a GDC STA, the GDC STA will have no information related to scanning operations. The present invention provides two methods for selecting an optimized bandwidth for initial scanning, e.g. during a boot-up procedure for the first time or during a system reset. The two methods can be performed separately or in combination, using some type of decision logic to determine which information to use when selecting the optimized bandwidth. This is not a limitation of the present invention and can be readily implemented by one skilled in the art. 
         [0013]    The following will detail both optimized bandwidth selection processes. This process is for when no previous information about bandwidths is available to the GDC dependent STA; for example, during a boot-up operation for the first time the GDC dependent STA is being operated. In this case, the GDC dependent STA only knows that it must scan for another STA on the TVWS band, but this band could be 6 MHz, 7 MHz or 8 MHz, depending on whether the GDC dependent STA is located in North America, Europe or Asia. 
         [0014]    Rather than scanning all bandwidths to search for AP beacons, the optimization procedure is used to quickly determine a most likely bandwidth. In a first embodiment, the GDC dependent STA will use statistical data of TVWS bands to determine which bandwidths are used in the most regions. The bandwidth which is used in the most regions is selected as the first bandwidth for scanning, followed by a bandwidth which is used in the next most regions, etc. 
         [0015]    In a second embodiment of the optimization procedure, a value can be set within the GDC dependent STA according to the country the GDC STA is produced in. This is because it is likely that a user will both purchase and operate a GDC dependent STA in the same country. When the GDC dependent STA starts a scanning procedure where there is no prior bandwidth information, the bandwidth corresponding to the country of sale will be selected as an optimized bandwidth. If, for example, the GDC dependent STA is bought in the United States, this information will be stored in a configuration file of the STA, and during boot-up, the 6 MHz bandwidth will be selected as a first scanning bandwidth. 
         [0016]    Using the above methods for selecting an optimized bandwidth, it is likely that an AP will be found quickly during an initial scan. The configuration file of the GDC dependent STA is non-volatile and can therefore store the bandwidth the AP is found on for subsequent procedures. When an AP is found on a different bandwidth from the optimized bandwidth, this information can be updated in the configuration file, and further used to generate statistical information related to how many APs have been found in subsequent scanning procedures and on which bandwidths. 
         [0017]    The above methods are illustrated in  FIG. 1A , steps  100 - 118 , which are detailed below. 
         [0018]    Step  100 : Does the GDC STA have any prior information about the optimized BW? If yes, go to Step  102 ; if no, go to Step  120 ; 
         [0019]    Step  102 : Does the GDC STA contain information in a configuration file detailing its country of sale? If yes, go to Step  104 ; if no, go to Step  108 ; 
         [0020]    Step  104 : Does the GDC STA need to determine first statistical data of TVWS bands? If no, go to Step  106 ; if yes, go to Step  108 ; 
         [0021]    Step  106 : Use the information in the configuration file to select an optimized bandwidth for scanning; 
         [0022]    Step  108 : Determine first statistical data of TVWS bands; 
         [0023]    Step  110 : Does the GDC STA use the information in the configuration file or the first statistical data to select an optimized bandwidth? If the information in the configuration file (CF) is used, go to Step  106 ; if the first statistical data (FSD) is used, go to Step  112 ; 
         [0024]    Step  112 : Use the first statistical data to select an optimized bandwidth to perform scanning; 
         [0025]    Step  114 : Is an AP beacon found? If yes, go to Step  118 ; if no, go to Step  116 : 
         [0026]    Step  116 : Use the first statistical data to select a next bandwidth for scanning; return to Step  114 ; 
         [0027]    Step  118 : Record the bandwidth of the AP beacon in the configuration file and go back to Step  100 ; 
         [0028]    As detailed above, once an AP beacon is located, the corresponding bandwidth will be recorded in the configuration file. This information can be used for subsequent scanning procedures, detailed herein as determining a prioritized bandwidth. In this case, the last-used bandwidth information as stored in the configuration file will be selected for a next scan. The GDC STA also maintains the statistical information related to how many APs have been found in subsequent scanning procedures and on which bandwidths. 
         [0029]    If no AP is found on the prioritized bandwidth, the statistical information is used to select a next bandwidth for further scanning, or to determine how many times the prioritized bandwidth has to be consecutively scanned before selecting a next bandwidth. 
         [0030]    The above is illustrated in  FIG. 1B , steps  120 - 130 , which are described below. 
         [0031]    Step  120 : Select a last previously used bandwidth as a prioritized bandwidth; 
         [0032]    Step  122 : Is an AP beacon found? If yes, go to Step  130 ; if no, go to Step  124 ; 
         [0033]    Step  124 : Determine second statistical data of the GDC STA; 
         [0034]    Step  126 : Does the second statistical data indicate to continue scanning on the same bandwidth? If yes, go back to Step  122 ; if no, go to Step  128 ; 
         [0035]    Step  128 : Select a next bandwidth for scanning according to the second statistical data; go back to Step  122 ; 
         [0036]    Step  130 : End. 
         [0037]    From the above, even when a GDC STA does not have the ability to determine its location or cannot use location information to contact with a geo-location database, the scanning procedure can still be simplified. 
         [0038]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.