Patent Publication Number: US-8971919-B2

Title: Fast generation of radio coverage map of access points in an indoor environment

Description:
REFERENCE TO CO-PENDING APPLICATIONS FOR PATENT 
     The present application for patent is related to the following co-pending U.S. patent application:
         “Efficient Generation of Radio Coverage Map of Access Points in an Indoor Environment” by Park et al., having Ser. No. 13/747,930, filed concurrently herewith, assigned to the assignee hereof, and expressly incorporated by reference herein.       

     FIELD OF DISCLOSURE 
     The presently disclosed embodiments are directed to the field of generating radio coverage maps of access points in an indoor environment. 
     BACKGROUND 
     A radio coverage map of an access point is a map of the signal strength of a signal transmitted by the access point as received at various locations on the map. Radio coverage maps of access points located in a building are important in indoor positioning. Radio coverage maps of access points located in the building are provided to a mobile station to assist the mobile station in determining its position. Using the radio coverage maps, the mobile station determines which access points to scan. The mobile station scans these access points and measures received signal strength indicator (RSSI) values from signals transmitted by these access points. The radio coverage map is also commonly called an RSSI heatmap. The radio coverage map is usually a three-dimensional radio coverage map. The radio coverage map is typically generated in advance by a server. Traditionally, the radio coverage map is generated by using the well-known dominant path model or ray tracing model. 
     Buildings such as malls and airports often have partial ceilings. In other words, two or more physical levels (i.e., floors or ceilings) of such building share the same top ceiling. If the partial ceilings are considered in the traditional process of generating the radio coverage maps of the access points located in such building (for example, by using the dominant path model or ray tracing model), this traditional process will require a very large amount of time and processing power. Thus, using the traditional process, it is not possible to generate quickly a radio coverage map of an access point located in such building, and it is not feasible for a mobile station, with its limited processing power, to generate a radio coverage map by itself. 
     SUMMARY 
     Exemplary embodiments of the invention are directed to systems and method for efficiently generating a radio coverage map of an access point in an indoor environment. 
     A method for generating a two-dimensional radio coverage map for an access point in a wireless environment comprising a plurality of physical levels including a first physical level and a second physical level is disclosed. A first radio coverage map comprising a plurality of original points is generated. Each of the original points has a first predicted value. The first radio coverage map is located above the second physical level and at a first distance from the access point. The access point is located above the second physical level. A target distance is selected to place a plurality of map points corresponding to the two-dimensional radio coverage map between the first physical level and the second physical level and at the target distance from the access point. Coordinates of the map points are generated by magnifying the first radio coverage map using the ratio of the target distance to the first distance. Each of the map points corresponds to one of the original points. An offset value representing an attenuation due to the target distance being different than the first distance is computed. For each of the map points, a predicted received signal strength value is generated by adding the offset value to the first predicted value of the corresponding one of the original points. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are presented to aid in the description of embodiments of the invention and are provided solely for illustration of the embodiments and not limitation thereof. 
         FIG. 1  is a diagram illustrating a system  100  in which one embodiment of the invention may be practiced. 
         FIG. 2  is a diagram illustrating a system  200  in which one embodiment of the invention may be practiced. 
         FIG. 3  is a diagram illustrating a system  300  in which one embodiment of the invention may be practiced. 
         FIG. 4  is a diagram illustrating a wireless environment  400  in which embodiments of the invention may be practiced. 
         FIG. 5  is a diagram illustrating an embodiment of the invention where a two-dimensional radio coverage map  440  is generated from a first radio coverage map  550 . 
         FIG. 6  is a flowchart illustrating a process of generating a radio coverage map for an access point in a wireless environment according to one embodiment. 
         FIG. 7  is a flowchart illustrating an embodiment of process  610  shown in  FIG. 6 . 
         FIG. 8  is a flowchart illustrating a process of determining approximately whether the access point is radio visible from the first physical level in a multi-level wireless environment. 
         FIG. 9  is a flowchart illustrating a process of generating a two-dimensional radio coverage map for an access point in a wireless environment according to one embodiment. 
         FIG. 10  is a diagram illustrating an apparatus according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the invention are disclosed in the following description and related drawings directed to specific embodiments of the invention. Alternate embodiments may be devised without departing from the scope of the invention. Additionally, well-known elements of the invention will not be described in detail or will be omitted so as not to obscure the relevant details of the invention. 
     One disclosed feature of the embodiments may be described as a process which is usually depicted as a flowchart, a flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process is terminated when its operations are completed. A process may correspond to a method, a program, a procedure, etc. One embodiment may be described by a schematic drawing depicting a physical structure. It is understood that the schematic drawing illustrates the basic concept and may not be scaled or depict the structure in exact proportions. 
     Embodiments of the invention are directed to apparatus and method for efficient generation of radio coverage map of an access point in an indoor environment. The technique provides a simplified process of generating a radio coverage map. The simplified process does not require much of processing power, thus can be performed by a mobile station. Employing the simplified process, either a location assistant server or a mobile station can quickly generate a radio coverage map for an access point. This is of particular benefit for a mobile station, since the mobile station can quickly determine which access points are most likely to be radio visible from the current coarse position of the mobile station. The mobile station can then focus on these most likely to be radio visible access points for scanning and measurement. An access point is radio visible to the mobile station if the signal strength of a signal transmitted by the access point as received at the current coarse position of the mobile station is sufficient for communication; in other words, the signal strength is above a predetermined minimum threshold. 
       FIG. 1  is a diagram illustrating a system  100  in which one embodiment of the invention may be practiced. The system  100  includes an access point management server  110 , an access point network  120 , a plurality of access points  130 , a location assistant server  140 , and a plurality of mobile stations  150 . The term “venue” is used herein to designate the local environment. The access point management server  110  receives information  102  from a venue operator or from information technology personnel. The information  102  includes map information of the venue, and information related to the access points located in the venue. The map information of the venue includes information regarding a structural layout of the wireless environment, and optionally includes information regarding material types of the plurality of physical levels (that is, ceilings, floors) in the venue. The information related to the access points located in the venue includes location information of the access points. The access point management server  110  uses the access point network  120  to communicate with the access points  130 . The access point management server  110  provides information  112  to the location assistant server  140 . The information  112  includes the map information of the venue, and the information related to the access points located in the venue. Based on the received information  112 , the location assistant server  140  generates radio coverage maps of the access points located in the venue. The location assistant server  140  receives requests for assistance from the mobile stations  150  and provides the radio coverage maps to the mobile stations  150 . Embodiments of the invention may be practiced by the location assistant server  140 . 
       FIG. 2  is a diagram illustrating a system  200  in which one embodiment of the invention may be practiced. The system  200  includes a location assistant server  240  and a plurality of mobile stations  250 . The location assistant server  240  receives information  212  directly from a venue operator and/or a public data contributor having access to map information of the venue and information related to the access points located in the venue. The information  212  includes map information of the venue, and information related to the access points located in the venue. The map information of the venue includes information regarding a structural layout of the wireless environment, and optionally includes information regarding material types of the plurality of physical levels (that is, ceilings, floors) in the venue. The information related to the access points located in the venue includes location information of the access points. Based on the received information  212 , the location assistant server  240  generates radio coverage maps of the access points located in the venue. The location assistant server  240  receives requests for assistance from the mobile stations  250  and provides the radio coverage maps to the mobile stations  250 . Embodiments of the invention may be practiced by the location assistant server  240 . 
       FIG. 3  is a diagram illustrating a system  300  in which one embodiment of the invention may be practiced. The system  300  includes a Web server  340 , the Internet or intranet  345 , and a plurality of mobile stations  350 . The Web server  340  receives information  312  from a venue operator. The information  312  includes map information of the venue, and information related to the access points located in the venue. The map information of the venue includes information regarding a structural layout of the wireless environment, and optionally includes information regarding material types of the plurality of physical levels (that is, ceilings, floors) in the venue. The information related to the access points located in the venue includes location information of the access points. The information  312  is saved at the Web server  340  and is accessible via a Uniform Resource Locator (URL). The mobile stations  350  may obtain this URL through known mobile applications. The mobile stations  350  may also obtain this URL by searching for beacons located in the venue. The beacons may be radio beacons (such as WiFi access point, Bluetooth access point) or visual beacons (such as Quick Response code, other types of matrix codes, and bar codes). Providing this URL to the Internet/Intranet  345 , the mobile stations  350  accesses and retrieves the information  312  stored at the Web server  340 . Based on the retrieved information  312 , the mobile stations  350  generate radio coverage maps of the access points located in the venue. Embodiments of the invention may be practiced by each of the mobile stations  350 . 
       FIG. 4  is a diagram illustrating a wireless environment  400  in which embodiments of the invention may be practiced. The wireless environment  400  comprises a first physical level  410  and a second physical level  420  located above the first physical level  410 . The wireless environment  400  includes an access point  430  located above the second physical level  420  at a distance  422  from the second physical level  420 . 
     A two-dimensional radio coverage map  440  located between the first physical level  410  and the second physical level  420  is generated by embodiments of the invention. The two-dimensional radio coverage map  440  is located at a target distance  442  from the access point  430 , and at a distance  412  from the first physical level  410 . The distance  412  is commonly referred to as the prediction height and ranges from 1 meter to 1.5 meters. This prediction height corresponds to a typical distance of a transceiver of a mobile station from the first physical level  410 . The two-dimensional radio coverage map  440  comprises a plurality of map points. Each of the map points has a predicted received signal strength value which representing a predicted received signal strength of a signal transmitted by the access point  430 . The two-dimensional radio coverage map  440  comprises a projected area  444  and a first area  446 . The first area comprises the map points that are located outside of the projected area  444 . The two-dimensional radio coverage map  440  may optionally include a second area  448  which is adjacent to the boundary of the projected area  444 , and comprises transition points. 
     A projection window  424  is located at a same vertical level as the second physical level  420 . The projection window may be an open space. The projection window  424  may also be an area having a specific material type which causes a specific attenuation to a received signal strength of a signal transmitted by the access point  430  and passing through the projection window  424 . For example, the specific material type may be wood, or metal, or concrete, etc. 
     The projected area  444  on the two-dimensional radio coverage map is generated by computing a geometrical projection from the access point  430  through the projection window  424  onto the two-dimensional radio coverage map  440 . 
       FIG. 5  is a diagram illustrating an embodiment  500  of the invention where the two-dimensional radio coverage map  440  is generated from a first radio coverage map  550 . The wireless environment comprises the first physical level  410  and the second physical level  420 , as described previously with respect to  FIG. 4 . 
     Referring to  FIG. 5 , a first two-dimensional radio coverage map  550  for the access point  430  is generated. In a wireless environment that includes more than two physical levels, the first two-dimensional radio coverage map is preferably at a prediction height above the physical level that is closest to the access point. The first two-dimensional radio coverage map  550  is located at a distance  552  from the access point  430 , and at a distance  554  (i.e., prediction height) from the second physical level  420 . The first two-dimensional radio coverage map  550  comprises a plurality of original points. Each of the original points has a predicted value representing a predicted received signal strength of a signal transmitted by the access point  430 . 
     The target distance  442  is selected to place the two-dimensional radio coverage map  440  at the target distance  442  from the access point  430 . Coordinates of the map points of the two-dimensional radio coverage map  440  are generated from coordinates of corresponding original points of the first two-dimensional radio coverage map  550 . A ratio of the target distance  442  to the first distance  552  is used to magnify the coordinates of an original point of the first two-dimensional radio coverage map  550  to obtain the coordinates of the corresponding map point of the two-dimensional radio coverage map  440 . In other words, coordinates of the map points of the two-dimensional radio coverage map  440  are generated by magnifying the first radio coverage map  550  using a ratio of the target distance  442  to the first distance  552 . An offset value representing an attenuation due to the target distance  442  being different than the first distance  552  is computed. For each of the map points of the two-dimensional radio coverage map  440 , a predicted received signal strength value is generated by adding the offset value to the predicted value of the corresponding one of the original points of the first two-dimensional radio coverage map  550 . 
       FIG. 6  is a flowchart illustrating a process  600  of generating a radio coverage map for an access point in a wireless environment according to one embodiment. The wireless environment comprises a plurality of physical levels including a first physical level and a second physical level located above the first physical level. 
     Referring to  FIG. 6  and  FIG. 4 , upon START, the process  600  generates a two-dimensional radio coverage map  440  located between the first physical level  410  and the second physical level  420  without taking into account a signal attenuation caused by the second physical level  420  (Block  610 ). The access point  430  is located above the second physical level  420 . The two-dimensional radio coverage map  440  is located at a target distance  442  from the access point  430  and comprises a plurality of map points. Each of the map points has a predicted received signal strength value. The process  600  determines a projection window  424  located at a same vertical level as the second physical level  420  (Block  620 ). Next, the process  600  determines a projected area  444  on the two-dimensional radio coverage map  440  by computing a geometrical projection from the access point  430  through the projection window  424  onto the two-dimensional radio coverage map  440  (Block  630 ). Then, the process  600  identifies a plurality of first points in a first area  446  on the two-dimensional radio coverage map  440  (Block  640 ). Each of the first points has a predicted received signal strength value. The first area  446  is outside the projected area  444 . Next, the process  600  reduces the predicted received signal strength value of each of the first points by a value equal to the signal attenuation caused by the second physical level  420  (Block  650 ). The process  600  is then terminated. 
       FIG. 7  is a flowchart illustrating an embodiment  700  of Block  610  shown in  FIG. 6 . The process  700  generates a two-dimensional radio coverage map  440  located between the first physical level  410  and the second physical level  420  without taking into account a signal attenuation caused by the second physical level  420 . 
     Referring to  FIG. 7  and  FIG. 4 , upon START, the process  700  generates coordinates for each of the map points on a two-dimensional plane corresponding to the two-dimensional radio coverage map  440  (Block  710 ). Then, the process  700  generates for each of the map points a predicted received signal strength value representing a predicted received signal strength of a signal transmitted by the access point  430  without taking into account the signal attenuation caused by the second physical level  420  (Block  720 ). The process  700  is then terminated. 
     Referring to Block  720  of  FIG. 7 , in one embodiment, the process  700  uses an equation corresponding to a simplified path loss model to generate for each of the map points a predicted received signal strength value. 
     In one embodiment, the process  700  uses the following equation corresponding to the simplified path loss model:
 
RSSI=RSSI0−10*pathLossExp*log 10 (dist2AP)
 
where:
         RSSI=predicted received signal strength value in dBm   RSSI 0 =received signal strength indicator at a distance of 1 meter from the access point in dBm=(wavelength/(4*π))^2*Ptx   where:   Wavelength=(speed of light)/(carrier frequency);   The wavelength is typically equal to 0.125 meters.   Ptx=transmission power;   Ptx ranges from −1 dBm to 20 dBm, and is nominally equal to 14 dBm. Any offset from the nominal value of transmission power is provided as a separate value in assistance information or broadcast by the access point in 802.11K protocol frames.   pathLossExp=path loss exponent;   pathLossExp is equal to 2 for free space, 1 to 5 for indoors environment, and typically is equal to 2.5.   dist2AP=distance from the map point being predicted to the position of the access point.       

     Referring to Block  620  of  FIG. 6  and  FIG. 4 , in determining a projection window  424  located at a same vertical level as the second physical level  420 , the process  600  determines a center of the projection window  424  and a plurality of points located on a perimeter of the projection window  424  (for example, the four corners of the projection window  424  as shown in  FIG. 4 ). The process  600  determines the projection window  424  by using information regarding a structural layout of the wireless environment. This information may also include information regarding material types of the plurality of physical levels of the wireless environment. Examples of material types are wood, concrete, metal, etc. 
     In one embodiment, the projection window  424  located at a same vertical level as the second physical level  420  is an open space. In other words, the second physical level  420  has an opening. In this embodiment, the process  600  determines an open space  424  located at a same vertical level as the second physical level  420 . 
     In another embodiment, the projection window  424  is not an open space and causes a second signal attenuation due to the material type of the projection window  424 . In this embodiment, the process  600  further comprises the operation of reducing the predicted received signal strength value of each of the map points that are located within the projected area  444  by a value equal to the second signal attenuation. 
     Referring to Block  640  of  FIG. 6  and  FIG. 4 , in one embodiment, the first area  446  on the two-dimensional radio coverage map  440  is adjacent to the projected area  444 . In other words, in this embodiment, the two-dimensional radio coverage map  440  has two areas that are adjacent to each other, namely, the projected area  444  and the first area  446 . 
     Referring to Block  640  of  FIG. 6  and  FIG. 4 , in another embodiment, the first area  446  on the two-dimensional radio coverage map is not adjacent to the projected area  444 . In this embodiment, the process  600  further comprises the operations of identifying a plurality of transition points in a second area  448  on the two-dimensional radio coverage map  440  that are located between the projected area  444  and the first area  446  and reducing the predicted received signal strength value of each of the transition points in the second area  448  by a value less than the signal attenuation caused by the second physical level  420 . For example, the predicted received signal strength value of each of the transition points may be reduced by a value equal to half of the signal attenuation caused by the second physical level  420 . The transition points in the second area  448  provide a smoother transition from the map points located within the projected area  444  to the map points located in the first area  446 , in terms of predicted signal strength values. In one implementation, the second area  448  forms a 5-meter area around the boundary of the projected area  444 . 
     Before generating the radio coverage map  440 , it may be advantageous to use a process to determine approximately whether the access point  430  is radio visible from the first physical level  410 . In the wireless environment shown in  FIG. 4 , the access point  430  is determined to be radio visible from the first physical level  410  if the signal attenuation caused by the second physical level  420  is less than or equal to a threshold. 
       FIG. 8  is a flowchart illustrating a process  800  of determining approximately whether the access point is radio visible from the first physical level, in a wireless environment where there are one or more third physical levels located above the second physical level and where the access point is located above the one or more third physical levels. 
     Upon START, the process  800  computes an aggregate value of signal attenuations caused by the second physical level and the one or more third physical levels (Block  810 ). Then, the process  800  compares the aggregate value to a threshold value (Block  820 ). If the aggregate value of signal attenuations is less than or equal to the threshold value, the process  800  determines that the access point is radio visible from the first physical level (Block  830 ). If the aggregate value of signal attenuations is greater than the threshold value, the process  800  determines that the access point is not radio visible from the first physical level (Block  840 ). The process  800  is then terminated. The process  800  may optionally include the operation of checking existence of an open space extending from the access point  430  to the first physical level  410 , using information regarding a structural layout of the wireless environment. 
     The process  800  is used first to determine the radio visibility of the access point from each of the physical levels of the multi-level wireless environment. Then, radio coverage maps are generated only for the physical levels from which the access point is radio visible. The process  800  is particularly beneficial for a mobile station, since the mobile station can quickly determine which access points are most likely to be radio visible from the current coarse position of the mobile station. 
       FIG. 9  is a flowchart illustrating a process  900  of generating a radio coverage map for an access point in a wireless environment according to one embodiment. The wireless environment comprises a plurality of physical levels including a first physical level and a second physical level. 
     For clarity of description,  FIG. 9  will be described with references to the example shown in  FIG. 5 . References made to the example shown in  FIG. 5  are only to illustrate one embodiment of the invention where a target distance  442  is greater than a first distance  552 . It is important to note that the process  900  is not limited to the illustrated example of  FIG. 5 . The process  900  is also applicable for the case where a two-dimensional radio coverage map is to be placed at a target distance that is smaller than the first distance at which a first radio coverage map is located from the access point. 
     Referring to  FIG. 9 , upon START, the process  900  generates a first radio coverage map  550  comprising a plurality of original points (Block  920 ). Each of the original points has a first predicted value. The first radio coverage map is located above the second physical level  420  and at a first distance  552  from the access point  430 . The access point  430  is located above the second physical level  420 . Next, the process  900  selects a target distance  442  to place a plurality of map points corresponding to the two-dimensional radio coverage map  440  between the first physical level  410  and the second physical level  420  and at the target distance  442  from the access point  430  (Block  930 ). Then, the process  900  generates coordinates of the map points by magnifying the first radio coverage map  550  using the ratio of the target distance  442  to the first distance  552  (Block  940 ). Each of the map points corresponds to one of the original points. Then, the process  900  computes an offset value representing an attenuation due to the target distance  442  being different than the first distance  552  (Block  950 ). Next, the process  900  generates for each of the map points a predicted received signal strength value by adding the offset value to the first predicted value of the corresponding one of the original points (Block  960 ). The process  900  is then terminated. 
     Referring to Block  920  of  FIG. 9 , the process of Block  920  may comprise the following operations. First, the process of Block  920  generates the plurality of original points corresponding to a two-dimensional plane located above the second physical level and at the first distance from the access point. Then, the process of Block  920  generates for each of the original points on the two-dimensional plane, a first predicted value representing a predicted received signal strength of a signal transmitted by the access point to produce the first radio coverage map  550  comprising the original points. 
     Alternately, the process of Block  920  may also generate a first radio coverage map by using an existing radio coverage map from a database as the first radio coverage map  550 . 
     Referring to Block  940  of  FIG. 9 , to generate coordinates of the map points by magnifying the first radio coverage map  550  using a ratio of the target distance  442  to the first distance  552 , the process  900  uses the following equations:
 
 x   i   =d   i   /d   0   *x   0 ;
 
 y   i   =d   i   /d   0   *y   0 ;
 
where:
 
     (x i , y i )=coordinates of one of the map points; 
     (x 0 , y 0 )=coordinates of a corresponding one of the original points; 
     d 0 =the first distance; 
     d i =the target distance. 
     It is important to note that, for the case where the target distance d i  is smaller than the first distance d 0 , the ratio d i /d 0  is less than 1 and the coordinates of the map points are generated by magnifying the first radio coverage map by a factor of less than 1. 
     Referring to  FIG. 5 , the first distance d 0  is the distance  552  from the access point  430  to the first radio coverage map  550 . As a numerical example, if the first radio coverage map  550  is placed at a distance  554  of 1 meter from the second physical level  420 , and the access point  430  is located at a distance  552  of 3.5 meters from the second physical level  420 , then the first distance d 0  is equal to 2.5 meters. 
     Referring to  FIG. 5 , the target distance d i  is the distance  442  from the access point  430  to the two-dimensional radio coverage map  440 . As a numerical example, if the two-dimensional radio coverage map  440  is placed at a distance  412  of 1 meter from the first physical level  410 , and the access point  430  is located at a distance  552  of 3.5 meters from the second physical level  420 , and the distance from the first physical level  410  to the second physical level  420  is 4 meters, then the target distance d 1  is equal to 6.5 meters. 
     Referring to Block  950  of  FIG. 9 , the process  900  computes an offset value representing an attenuation due to the target distance  442  being different than the first distance  552  using the following equation:
 
RSSIOffset i =10*pathLossExp*log 10 ( d   0   /d   i )
 
where:
 
     RSSIOffset i =the offset value; 
     pathLossExp=path loss exponent; 
     d 0 =the first distance; 
     d i =the target distance. 
     The process  900  may be used as an embodiment of the process  610  shown in  FIG. 6  of generating a two-dimensional radio coverage map  440  located between the first physical level  410  and the second physical level  420  without taking into account a signal attenuation caused by the second physical level  420 . 
     In the case where simplicity is preferred at the expense of accuracy, the projection window  424  and the projected area  444  are not determined. In such case, the process  900  can be used separately from the process  600  as an alternate way of generating a two-dimensional radio coverage map for the access point  430  as follows. First, the process  900  is performed as described previously. Then, an additional operation of reducing the predicted received signal strength value of each of the map points by a value equal to the signal attenuation caused by the second physical level  420  is performed. In the case where the wireless environment comprises one or more third physical levels located between the first physical level  410  and the second physical level  420 , after the process  900  is performed, an additional operation of reducing the predicted received signal strength value of each of the map points by a value representing an aggregation of signal attenuations caused by the second physical level and the one or more third physical levels is performed. 
     The methods, sequences and/or algorithms described in connection with the embodiments disclosed herein can be practiced for any number of physical levels in an indoor environment. For example, if there is an access point in the space above the fourth physical level of a building, embodiments of the invention can be used to generate radio coverage maps for the first, second, third, or fourth physical levels of the building and to quickly determine whether the access point is radio visible at any of those physical levels. 
       FIG. 10  is a diagram illustrating an apparatus  1000  according to one embodiment. The apparatus  1000  may be included in the location assistant server  140  of  FIG. 1 , in the location assistant server  240  of  FIG. 2 , or in one of the mobile stations  350  of  FIG. 3 . The apparatus  1000  includes a processor  1010 , a chipset  1020 , a memory  1030 , an interconnect  1040 , a mass storage medium  1050 , and an input/output (I/O) interface  1060 . The apparatus  1000  may include more or less components than the above components. 
     The processor  1010  represents a central processing unit of any type of architecture, such as processors using hyper threading, security, network, digital media technologies, single-core processors, multi-core processors, embedded processors, mobile processors, micro-controllers, digital signal processors, superscalar computers, vector processors, single instruction multiple data (SIMD) computers, complex instruction set computers (CISC), reduced instruction set computers (RISC), very long instruction word (VLIW), or hybrid architecture. 
     The chipset  1020  provides control and configuration of memory and input/output devices such as the memory  1030 , the mass storage medium  1050  and the I/O interface  1060 . The chipset  1020  may integrate multiple functionalities such as graphics, media, host-to-peripheral bus interface, memory control, power management, etc. It may also include a number of interface and I/O functions such as peripheral component interconnect (PCI) bus interface, processor interface, interrupt controller, direct memory access (DMA) controller, power management logic, timer, system management bus (SMBus), universal serial bus (USB) interface, mass storage interface, low pin count (LPC) interface, wireless interconnect, direct media interface (DMI), etc. 
     The memory  1030  stores code and data. The memory  1030  is typically implemented with dynamic random access memory (DRAM), static random access memory (SRAM), or any other types of memories including those that do not need to be refreshed. The memory  1030  may include a radio coverage map generation module  1035  that performs all or portion of the operations described above. 
     The interconnect  1040  provides interface to peripheral devices. The interconnect  1040  may be point-to-point or connected to multiple devices. For clarity, not all interconnects are shown. It is contemplated that the interconnect  1040  may include any interconnect or bus such as Peripheral Component Interconnect (PCI), PCI Express, Universal Serial Bus (USB), Small Computer System Interface (SCSI), serial SCSI, and Direct Media Interface (DMI), etc. 
     The mass storage medium  1050  includes interfaces to mass storage devices to store archive information such as code, programs, files, data, and applications. The mass storage interface may include SCSI, serial SCSI, Advanced Technology Attachment (ATA) (parallel and/or serial), Integrated Drive Electronics (IDE), enhanced IDE, ATA Packet Interface (ATAPI), etc. The mass storage device may include compact disk (CD) read-only memory (ROM), digital video/versatile disc (DVD), floppy drive, hard drive, tape drive, and any other magnetic or optic storage devices. The mass storage device provides a mechanism to read computer-readable media. In one embodiment, the mass storage medium  1050  may include flash memory. 
     The I/O interface  1060  provides interface to I/O devices such as the panel display or the input entry devices. The I/O interface  1060  may provide interface to a touch screen in the graphics display, the keypad, and other communication or imaging devices such as camera, Bluetooth interface, etc. 
     The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Likewise, the term “embodiments of the invention” does not require that all embodiments of the invention include the discussed feature, advantage or mode of operation. The “computer-readable medium” may include any medium that may store or transfer information. Examples of the computer-readable medium include an electronic circuit, a semiconductor memory device, a read only memory (ROM), a flash memory, an erasable programmable ROM (EPROM), a floppy diskette, a compact disk (CD) ROM, an optical disk, a hard disk, etc. The computer-readable medium may be embodied in an article of manufacture. The computer-readable medium may include information or data that, when accessed by a processor, cause the processor to perform the operations or actions described above. The computer-readable medium may also include program code, instruction or instructions embedded thereon. The program code may include computer-readable code, instruction or instructions to perform the operations or actions described above. The term “information” or “data” here refers to any type of information that is encoded for computer-readable purposes. Therefore, it may include program, code, data, file, etc. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of embodiments of the invention. As used herein, the singular forms “a”, “an”, and “the”, are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes”, and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Further, many embodiments are described in terms of sequences of actions to be performed by, for example, elements of a computing device. It will be recognized that various actions described herein can be performed by specific circuits (e.g., application specific integrated circuits (ASICs)), by program instructions being executed by one or more processors, or by a combination of both. Additionally, these sequences of actions described herein can be considered to be embodied entirely within any form of computer-readable medium having stored therein a corresponding set of computer instructions that, upon execution, would cause an associated processor to perform the functionality described herein. Thus, the various aspects of the invention may be embodied in a number of different forms, all of which have been contemplated to be within the scope of the claimed subject matter. In addition, for each of the embodiments described herein, the corresponding form of any such embodiments may be described herein as, for example, “logic configured to” perform the described action. 
     Further, all or part of an embodiment may be implemented by various means depending on applications according to particular features, functions. These means may include hardware, software, or firmware, or any combination thereof. A hardware, software, or firmware element may have several modules coupled to one another. A hardware module is coupled to another module by mechanical, electrical, optical, electromagnetic or any physical connections. A software module is coupled to another module by a function, procedure, method, subprogram, or subroutine call, a jump, a link, a parameter, variable, and argument passing, a function return, etc. A software module is coupled to another module to receive variables, parameters, arguments, pointers, etc. and/or to generate or pass results, updated variables, pointers, etc. A firmware module is coupled to another module by any combination of hardware and software coupling methods above. A hardware, software, or firmware module may be coupled to any one of another hardware, software, or firmware module. A module may also be a software driver or interface to interact with the operating system running on the platform. A module may also be a hardware driver to configure, set up, initialize, send and receive data to and from a hardware device. An apparatus may include any combination of hardware, software, and firmware modules. 
     Those of skill in the art will appreciate that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     Further, those of skill in the art will appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. 
     The methods, sequences and/or algorithms described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. 
     Accordingly, an embodiment of the invention can include a computer-readable medium embodying a method for efficient generation of radio coverage map of an access point. Accordingly, the invention is not limited to illustrated examples and any means for performing the functionality described herein are included in embodiments of the invention. 
     While the foregoing disclosure shows illustrative embodiments of the invention, it should be noted that various changes and modifications could be made herein without departing from the scope of the invention as defined by the appended claims. The functions, steps and/or actions of the method claims in accordance with the embodiments of the invention described herein need not be performed in any particular order. Furthermore, although elements of the invention may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.