Abstract:
Low signal strength areas in a communication system are identified utilizing a mobile unit. The mobile unit receives a first signal. If the first signal falls below a predetermined signal strength threshold the mobile unit determines and stores its geographic location. Upon receiving a second signal that exceeds the predetermined signal strength threshold the mobile unit sends the geographic location to the second base station.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to communication systems, and more particularly to cellular network coverage. 
       BACKGROUND OF THE INVENTION 
       [0002]    Cellular service providers provide cellular service to subscribers over a wide-ranging coverage area. This service is provided by installing multiple base stations within the coverage area, each base station providing communication within a cell. Each base station sends and receives over-the-air signals to mobile units within their cell. 
         [0003]    Cells generally overlap so that mobile units do not lose coverage when moving within the coverage area from one cell to another. 
         [0004]    One common problem in cellular networks is dropped calls, which occur when a mobile unit engaged in communication loses the signal from the base station to which it had been communicating. This can occur due to a poor network plan, equipment malfunction, or intermittent weather conditions. 
         [0005]    In addition, cellular service providers manage their networks by splitting cells with multiple base stations or adding additional base stations. The impact of these actions has an effect on the coverage provided, and the service provider requires knowledge of the impact on the quality of their network. 
         [0006]    In current cellular systems, service providers detect coverage holes by monitoring dropped calls, logging customer complaints, or having technicians move through the cellular system measuring signal strength. Each of these methods has significant drawbacks. Dropped calls are not always the result of moving out of cell coverage, and it is not always possible to determine an accurate location of a cell boundary. Customers do not always complain about dropped calls, and when they do they typically do not provide an accurate location description. Technicians provide a more accurate testing but are expensive. 
         [0007]    Therefore, a need exists for a method to simply and accurately determine coverage holes in a cellular communication system. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    Mobile units, such as GPS enabled smart phones, are updated to detect low signal-strength and/or loss of service for both voice and data, and record the location of the event. Once service is restored, the mobile unit sends a message containing the event to a Cellular Coverage Monitor. The Cellular Coverage Monitor correlates the event with data from the MSC and displays a map showing a service provider&#39;s network coverage. 
         [0009]    The coverage data can be used by the service provider for planning extensions to the cellular network. The area with the highest number of customers losing service could be expanded first. The coverage data could also alert the service provider to unexpected loss of service. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0010]      FIG. 1  depicts a portion of a communication system in accordance with an exemplary embodiment of the present invention. 
           [0011]      FIG. 2  depicts a flowchart of the patentable process that occurs meaningfully within various physical devices within communication system in accordance with an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    An exemplary embodiment of the present invention can be better understood with reference to  FIGS. 1 and 2 .  FIG. 1  depicts a portion  100  of a communication system in accordance with an exemplary embodiment of the present invention. Portion  100  includes three base stations, base station  101 , base station  102 , and base station  103 , two Mobile Switching Centers (MSC), MSC  104  and MSC  105 , a cellular coverage monitor  106 , and a Service Coverage Display  107 . Portion  100  communicates with mobile unit  110  and GPS satellite  108 . 
         [0013]    In an exemplary embodiment, base stations  101 ,  102 , and  103  are CDMA base stations and MSC  104  and MSC  105  are CDMA MSCs. MSC  104  and MSC  105  control base stations  101 ,  102 , and  103 . It should be understood that a typical communication system includes more than three base stations and two mobile switching centers, but these amounts are shown for clarity. 
         [0014]    Cellular coverage monitor (CCM)  106  is a computer that is able to receive location and service data from mobile unit  110 , preferably via an SMS message. Alternately CCM  106  receives the location and service data via a message sent via a base station and an MSC. CCM  106  also includes a processor for processing and correlating data received, memory for storing data, and an output port for outputting data. CCM  106  can be a stand-alone unit or could be included in an MSC or an NOC (Network Operations Center). 
         [0015]    Service Coverage Display (SCD)  107  is an output device that displays, preferably via a graphical user interface, data from CCM  106 . SCD  107  can be a monitor or the like. SCD  107  can be a stand-alone unit or can be incorporated into CCM  106 . 
         [0016]    GPS satellite  108  depicts one of several space-based global navigation satellite system that provides reliable location and time information anywhere on or near the Earth. Although only one satellite is depicted for clarity, the GPS system includes a plurality of satellites and a user needs to have an unobstructed line of sight to four or more GPS satellites. 
         [0017]    In accordance with an exemplary embodiment, mobile unit  110  is GPS-enabled. At a first time mobile unit  110  is located within the coverage area of base station  101 . At a second time mobile unit  110  is located within the coverage area of base station  103 . 
         [0018]    In the exemplary embodiment depicted in  FIG. 1 , as mobile unit  110  leaves the coverage area of base station  101 , mobile unit  110  detects that it has lost the service of base station  101 . Upon detecting this loss of service, mobile unit  110  determines and stores its current location. In an exemplary embodiment, the current location is determined using GPS and includes the latitude, longitude, and altitude of mobile station  110  at the time it lost service. Mobile unit  110  can determine and store this location data for voice service and alternately for data service. 
         [0019]    Upon recovering service, in this exemplary embodiment when mobile unit  110  enters the coverage area of base station  103  and has adequate cellular service, mobile unit  110  sends the location data to cellular coverage monitor  106 . In an exemplary embodiment, mobile unit  110  sends the location data via a loss of service event and sends the loss of service event to cellular coverage monitor  106  via base station  103  and MSC  105 . 
         [0020]    In an exemplary embodiment, cellular coverage monitor  106  queries MSC  104  and MSC  105  for mobile unit data to correlate the service loss. CCM  106  can use the location data to determine which MSC is associated with a particular location and use that information to determine which MSC to query. 
         [0021]    After correlating with MSC location data and other service loss events, cellular coverage monitor  106  updates service coverage display  107 . 
         [0022]      FIG. 2  depicts a flowchart of the patentable process that occurs meaningfully within various physical devices within communication system  100 . In accordance with an exemplary embodiment, mobile unit  110  is a smart phone that can be dynamically updated with an updateable list of service thresholds. Each threshold preferably includes a service type and a signal strength. In an exemplary embodiment, the service type is either voice or data. 
         [0023]    Mobile unit  110  detects ( 201 ) a change in the received signal level. In accordance with an exemplary embodiment, the signal level relates to the signal received by mobile unit  110  from base station  101 . 
         [0024]    Upon detecting a change in signal strength, mobile unit  110  determines ( 202 ) if the new signal level is below a predetermined threshold. If the new signal level does not fall below the predetermined threshold, the process ends ( 299 ). 
         [0025]    If the new signal does fall below the predetermined threshold as determined at step  202 , mobile unit  110  records ( 203 ) signal strength measurements and location parameters. In an exemplary embodiment, the location parameters include the latitude, longitude, and altitude of mobile station  110  when it received the new signal. 
         [0026]    In an exemplary embodiment, mobile unit  110  received the new signal and the new signal fell below a predetermined threshold. The predetermined threshold is set at a level of inadequate service. For example, it can be set at a level of lower than acceptable service. Alternately, the predetermined threshold can be set at a level where service is interrupted and a call or data session is ended. 
         [0027]    Upon receiving acceptable service, mobile unit  110  sends ( 204 ) the signal strength measurements and the location parameters to Cellular Coverage Monitor  106 . In an exemplary embodiment, mobile unit  110  sends an event to Cellular Coverage Monitor  106 , and the event includes the signal strength measurements and the location parameters. 
         [0028]    If it is determined ( 205 ) that the sending succeed at step  204 , the process ends ( 299 ). If the sending did not succeed at step  204 , mobile unit  110  saves ( 206 ) the event for sending at a later time. In an exemplary embodiment, the sending is done when service is available to mobile unit  110 . 
         [0029]    An exemplary embodiment of the present invention thereby provides a low-cost and accurate way of mapping service levels in a cellular network and will provide the service provider an automatic way of monitoring the quality of its network. It will show the service provider where to expand its network and where unexpected problems exist. This is accomplished without requiring drive testing, which if performed on the entire network would be very expensive. This solution is better than tracking dropped calls or customer complaints, because it detects service levels even when not in a call and provides accurate location. This solution provides thousands of data points at minimal cost to the service provider. 
         [0030]    While this invention has been described in terms of certain examples thereof, it is not intended that it be limited to the above description, but rather only to the extent set forth in the claims that follow.