Abstract:
Described is a system including first and second access points and a switch. The first access point transmits a radio frequency signal. The second access point receives the signal and detects a signal strength of the signal. The switch receives the signal strength from the second access point and generates output data as a function of the signal strength and a predetermined signal strength. The switch executes a predetermined procedure which corresponds to the output data.

Description:
BACKGROUND INFORMATION  
       [0001]     During design or deployment of a wireless network, a placement of access points/ports (“APs”) is critical to ensuring a resilient radio frequency (“RF”) coverage throughout the network. However, the network is frequently utilized in a physical landscape (e.g., a retail store, a warehouse) in which changes thereto may cause the RF coverage to be weakened or completely lost. For example, a post design/deployment change (e.g., adding, removing and/or rearranging items) within the landscape may result in a weaker signal transmitted and/or received by the APs.  
         [0002]     In anticipation of the change(s), a network administrator, during design and simulation of the network, may attempt to compensate for the landscape of the network when using a network-design software. However, a simulation of the network is only as good as an input received (e.g., a floor plan). That is, the floor plan may not provide an accurate model, because it may not account for RF propagation characteristics of items therein (e.g., walls, doors, windows) and any changes which are made to the network after deployment.  
         [0003]     After deployment, the network administrator may utilize a trial-and-error approach by repeatedly repositioning the APs until a satisfactory result is obtained (e.g., a strong signal strength). This approach is problematic in that it requires a significant amount of time, during which, the network may be operating at a reduced efficiency.  
         [0004]     Even after installation of the APs, the AP may experience a partial or a total failure. For example, a directional antenna of the AP may become dislodged or redirected. Also, the AP may have been installed adjacent to an object (e.g., a metal structure) which would diminish RF propagation characteristics of the signals to/from the AP. Thus, there is a need for identifying these conditions during operation of the network (i.e., after design and/or installation).  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention relates to a system including first and second access points and a switch. The first access point transmits a radio frequency signal. The second access point receives the signal and detects a signal strength of the signal. The switch receives the signal strength from the second access point and generates output data as a function of the signal strength and a predetermined signal strength. The switch executes a predetermined procedure which corresponds to the output data. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is an exemplary embodiment of a system according to the present invention;  
         [0007]      FIG. 2  is an exemplary embodiment of a signal table according to the present invention;  
         [0008]      FIG. 3  is an exemplary embodiment of a method according to the present invention; and  
         [0009]      FIG. 4  is an exemplary embodiment of another system according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0010]     The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are provided with the same reference numerals. The present invention provides a system and a method for evaluating operation of a wireless device in a wireless network. An exemplary embodiment of the present invention will be described in the context of an enclosed space (e.g., a store, a warehouse, etc.). However, one skilled in the art will understand that the present invention is not limited to such a space, but may be utilized in any environment which employs the wireless network.  
         [0011]      FIG. 1  shows an exemplary embodiment of a system  1  deployed in the space according to the present invention. The system  1  may include a network management arrangement (e.g., a switch  14 ) coupled to a communications network  12 . The switch  14  may include one or more components and/or devices for sending and receiving a data request, and may further include a storage medium (e.g., a memory) or be coupled to a stand-alone storage device (e.g., a database). The switch  14  may store data about the network  12  including an operational status, an RF coverage area, a MAC address and a physical location of each wireless device connected to the network  12 . This data may be utilized for management and evaluation of the network  12 , as will be described below. The network  12  may be any communications network (e.g., LAN, WAN, Internet, etc.) comprising one or more infrastructure components (e.g., hubs, switches, servers, etc.).  
         [0012]     The switch  14  may be coupled to one or more access points/ports (“APs”)  20 , 22 , 24  which provide a wireless connection for one or more mobile units to the network  12 . That is, the APs  20 - 24  may be any device which converts a packet format from a wired communication protocol (e.g., TCP/IP) to a wireless communication protocol (e.g., an 802.11 protocol), and vice-versa. Those of skill in the art will understand the mobile unit may be, for example, an image- or laser-based scanner, an RFID reader, a cell phone, a laptop, a network interface card, a handheld computer, a PDA, etc. Further understood by those of skill in the art is that any number of APs may be coupled to the switch  14 .  
         [0013]     While the present invention will be described with reference to the system  1  shown in  FIG. 1 , other embodiments of the system may be implemented. For example,  FIG. 4  shows a exemplary system  400  which may be utilized in accordance with the present invention. Similar to the system  1 , the system  400  may be deployed in a space  410 , such as, for example, a store or a warehouse. In this embodiment, a plurality of APs  415 - 440  are deployed throughout the space  410  with a goal of providing resilient wireless coverage to any mobile unit operating therein. Thus, radio frequency (“RF”) coverage areas (shown as circles around the APS  415 - 440 ) may overlap. As such, a signal transmitted by one AP (e.g., AP  420 ) may be heard by one or more of the APs  415 ,  425 - 440  if they are tuned to a same channel as the AP  420 . A switch may be coupled to each of the APs  415 - 440  and evaluate operation of each in accordance with the present invention.  
         [0014]     Referring back to  FIG. 1 , the AP  20  may broadcast a wireless signal (e.g., a beacon) at a predetermined interval (e.g., every 100 ms). Those of skill in the art will understand that while the present invention will be explained with respect to the AP  20 , the APs  24  and  26  and any further APs may be utilized. Further, between a transmission of the beacon and a subsequent beacon, the AP  20  may communicate with the mobile unit, the APs  24  and  26  and/or the switch  14 .  
         [0015]     Each AP which is tuned to a same RF channel as the AP  20  may receive the beacon. For example, the AP  24  may be tuned to the channel and receive the beacon(s) broadcasted by the AP  20 . According to the present invention, upon receipt of the beacon, the AP  24  may identify a signal data of the beacon which may include a signal strength thereof. The AP  24  may record and store the signal data in a signal table  200 , as shown in  FIG. 2 . In one embodiment, the signal table  200  may be a management information base (“MIB”) which may include a primary index  215  indicative of the AP which transmitted the beacon (e.g., the AP  20 ) and a secondary index  220  including one or more data entries indicative of one or more characteristic(s) of the beacon and a prior beacon(s) from the AP (e.g., the AP  20 ).  
         [0016]     The data entries may be included as branches of the secondary index  220 . The data entries may include the signal data which is indicative of the one or more characteristics of one or more beacons transmitted by the AP  20  and received by the AP  24 . For example, the data entries may include the signal data corresponding to a number of beacons received, a strongest/weakest signal strength of the beacons, a sum of the signal strengths of the beacons, a sum of squares of the signal strengths of the beacons and a signal strength of a most recently received beacon. In this manner, each AP may include a unique signal table including the signal data for the beacon(s) received thereby.  
         [0017]     In operation, when the beacon is received, the AP  24  may update the signal data in the signal table  200 . For example, the AP  24  may input the signal strength of the beacon as the signal strength of the most recently received beacon (e.g., in a “MostRecent” data entry). The AP  24  may incorporate the signal strength into the sum and the sum of squares of the signal strengths. The AP  24  may further determine whether the signal strength is a best (i.e., strongest) or a worst (i.e., weakest) of all prior beacons which have been received from the AP  20 . If so, the signal strength may be inputted into a “BestSignalStrength“field or a “WorstSignalStrength” field. Thus, the AP  24  may continually update the signal table  200  after receipt of each beacon from any AP which is transmitting on the same channel as the AP  24 .  
         [0018]     The switch  14  may utilize the signal data to evaluate operation of the APs  20 - 24 . In one embodiment, the switch  14  utilizes a predetermined network management protocol (e.g., a Simple Network Management Protocol (“SNMP”)) to harvest the signal data from the APs  20 - 24 , which may be SNMP-compliant devices. In this embodiment, the switch  14  may be provided with and/or request the signal data from the APs  20 - 24 .  
         [0019]     Upon receipt of the signal data, the switch  14  may compare the signal data to stored data. In one embodiment, the stored data may include simulation data obtained from a simulation of the RF environment generated by, for example, the network design software. The software may take into account a type (e.g., a power-setting, an RF range, etc.) and a location of each AP, a physical environment of the network (e.g., layout, walls, windows, doors, etc.) and RF propagation characteristics of the physical environment. In another embodiment, the stored data may include deployment data collected after deployment of the network. For example, the APs  20 - 24  may generate the signal table  200  and gather the deployment data after deployment of the network and report the deployment data to switch  14 , which stores the deployment data as the stored data. In a further embodiment, the stored data may include operational data collected during operation of the network. As understood by those of skill in the art, the operational data may conform most closely to the signal data.  
         [0020]     The comparison of the signal data to the stored data may generate output data which may be indicative of a predetermined condition (e.g., input to the network design software was incomplete). For example, an actual physical environment may differ from a designed physical environment due to construction difficulties (e.g., a wall could not be built). Thus, the simulation of the RF environment would not have accounted for a component(s) of the actual physical environment which differs from the designed physical environment. Thus, the output data may be indicative of a difference between the designed and actual physical environments.  
         [0021]     The output data may further indicate that the APs are not installed in their corresponding predetermined locations. That is, the simulation may include the predetermined location of each AP in the network, whereas an actual location of the AP may differ therefrom. For example, when the AP  20  was being installed, it may have been affixed to a wall rather than a ceiling, as intended. Also, the AP  20  may have one or more directional antennas, which may have been incorrectly oriented (e.g., upside-down) during or after installation. Either of these instances may alter the RF propagation characteristics of the AP  20 .  
         [0022]     Furthermore, the output data may be indicative of a post-installation change. For example, the AP  20  may become dislodged, the antenna may be unintentionally re-oriented and/or items may be stacked around the AP  20 . The post-installation change may also alter the RF propagation characteristics of the AP  20 .  
         [0023]     During operation of the network, the switch  14  may compare the signal data to the stored data to generate the output data, and evaluate performance of the APs as a function of the output data. The signal data may be used to verify the simulation of the RF environment and/or detect installation errors, changes in the physical environment which affect the RF environment and/or failures/malfunctions of the APs. When the performance of the AP falls below a threshold, the switch  14  may execute a predetermined action such as, for example, alerting an administrator and/or maintenance staff.  
         [0024]      FIG. 3  shows an exemplary embodiment of a method  300  according to the present invention. In step  305 , the AP  24  receives the beacon transmitted by the AP  20 . As stated above, the AP  24  may hear the beacon(s) of any AP which is transmitting on the RF channel to which the AP  24  is currently tuned. Thus, those of skill in the art will understand that the AP  24  may receive a plurality of beacons from a corresponding plurality of APs, and list each AP in the primary index  215  of the signal table  200 .  
         [0025]     In step  310 , the AP  24  updates the signal table  200  with the signal data from the beacon. The “MostRecent” field may be updated after each beacon is received from the AP  20 . The AP  24  may then determine whether to update the “BestSignalStrength” and/or the “WorstSignalStrength” fields.  
         [0026]     In step  315 , the signal data is provided to the switch  14 . The switch  14  may harvest the signal data from the APs  20 - 24  at a predetermined time/interval. That is, the switch  14  may transmit a request for the signal data to each of the APs  20 - 24 . As described above, the request and a resulting response (including the signal data) from the APs may be executed according to the SNMP.  
         [0027]     In step  320 , the switch  14  compares the signal data to the stored data to generate the output data which may be indicative of a problem with the AP  20 . In one exemplary embodiment, the switch  14  compares the signal strength of the beacon to a stored signal strength which may be a predetermined range and/or value (e.g., a minimum signal strength). When the signal strength is within the predetermined range and/or greater than the value, the method  300  returns to step  305  whereby the AP  24  receives a further beacon from the AP  20 .  
         [0028]     In step  325 , the signal strength is outside of the predetermined range, so the switch  14  executes a predetermined response. In one embodiment, the switch  14  may transmit an alert to a server notifying a network administrator that a problem may exist with respect to the AP  20 . The alert may include a location of the AP  20  and a problem type (e.g., low signal strength, erroneous antenna orientation, etc.). The alert may indicate that the AP  20  has experienced a partial or total malfunction and/or is emitting a weak signal. In another embodiment, the switch  14  may take the AP  20  offline and boost power to the APs  22  and  24  to extend the RF coverage areas thereof compensating for a removal of the AP  20 .  
         [0029]     The present invention may provide an advantage of a real-time assessment of the APs  20 - 24  while in operation. In this manner, the network administrator may be notified when a performance of the AP drops below a simulated/expected performance. Thus, the AP may be repaired and/or replaced to maintain an integrity of the RF environment.  
         [0030]     The present invention has been described with the reference to the above exemplary embodiments. One skilled in the art would understand that the present invention may also be successfully implemented if modified. Accordingly, various modifications and changes may be made to the embodiments without departing from the broadest spirit and scope of the present invention as set forth in the claims that follow. The specification and drawings, accordingly, should be regarded in an illustrative rather than restrictive sense.