Abstract:
The present specification describes techniques and apparatus that enable location-based detection of interference. In one or more implementations, a neighboring cell generating interference for a mobile device is determined based at least in part on a location of the mobile device.

Description:
RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/087,842, filed on Aug. 11, 2008, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     Use of cellular devices has become commonplace. Generally, in a cellular communications system, multiple base stations are set up that each provide a separate area of coverage. Each separate area of coverage is commonly referred to as a cell. Mobile devices that are physically located within a particular cell communicate with the base station responsible for that cell. Situations can arise, however, in which signals from a mobile device physically located in one cell are received by a base station responsible for a different cell. These signals can be a source of interference for other mobile devices communicating with that base station. 
     SUMMARY 
     A method implemented in a first cellular base station located within a cell is described. The method includes analyzing signals received from a mobile device to identify when interference for the mobile device exceeds a threshold amount, the mobile device being managed by the first cellular base station. The method further includes, in response to the interference for the mobile device exceeding the threshold amount, determining a location of the mobile device in the cell, and determining a neighboring cell generating the interference for the mobile device based on the location of the mobile device in the cell. 
     A computing device of a cellular base station is also described. The computing device includes a communicator to receive signals from multiple mobile devices being managed by the cellular base station; an analyzer to analyze the signals and identify when signals from one or more of the multiple mobile devices are being interfered with by greater than a threshold amount; and a locator to determine, based on a location of the one or more mobile devices, a cell responsible for the interference. 
     Another method implemented in a first cellular base station is also described, and includes identifying when interference in signals received from a mobile device exceeds a threshold amount, the mobile device being located in a first cell being managed by the first cellular base station; determining a second cell closest to the mobile device; and requesting that a second cellular base station that manages the second cell attempt to reduce the interference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The same numbers are used throughout the drawings to reference like features. 
         FIG. 1  illustrates an example cellular communications system implementing the location-based detection of interference in cellular communications systems. 
         FIG. 2  is a flowchart illustrating an example process for implementing the location-based detection of interference in cellular communications systems. 
         FIG. 3  is a flowchart illustrating another example process for implementing the location-based detection of interference in cellular communications systems. 
         FIG. 4  is a generalized example of a computing device that can be used to implement the location-based detection of interference in cellular communications systems. 
     
    
    
     DETAILED DESCRIPTION 
     Location-based detection of interference in cellular communications systems is discussed herein. Generally, a base station responsible for managing mobile devices for a cell in a cellular communications system analyzes signals received from the mobile devices that base station is managing. The base station determines, based on a signal-to-noise ratio value or other interference measurement calculated for signals received from a mobile device, whether interference in the signal received from the mobile device exceeds a threshold amount. This threshold amount can be exceeding of a particular value for a particular amount of time. If the interference exceeds the threshold amount, then the base station determines that the mobile device is being interfered with by one or more mobile devices in another cell. In response, the base station determines a closest neighboring cell of the mobile device being interfered with, and communicates a request to the base station responsible for managing mobile devices in that neighboring cell. The request that is sent requests that the base station responsible for managing mobile devices in that neighboring cell reduce the interference being generated by the mobile devices in that neighboring cell. 
       FIG. 1  illustrates an example cellular communications system  100  implementing the location-based detection of interference in cellular communications systems in accordance with one or more embodiments. System  100  includes four cells  102 ,  104 ,  106 , and  108 . For ease of explanation, only four cells are illustrated in  FIG. 1 . However, cellular communications system  100  can include a different number of cells. A cellular communications system  100  can be implemented using a variety of different conventional technologies and/or protocols, such as any of the GSM (Global System for Mobile Communications)-based systems, CDMA (Code Division Multiple Access)-based systems, AMPS (Advanced Mobile Phone System)-based systems, and so forth. 
     Within each cell  102 ,  104 ,  106 , and  108  is a cellular base station  112 ,  114 ,  116 , and  118 , respectively. Each cell represents a geographic or physical area covered or managed by the cellular base station within that cell. The size and shape of each cell can vary based on, for example, the technologies and/or protocols used by the cellular base stations, the power of the cellular base stations, the physical terrain of the area covered by the cellular base station, interfering signals received from other sources within and/or external to the cell, and so forth. 
     Mobile devices are located within different cells and can move between cells. In the example of  FIG. 1 , mobile devices  132 ,  134 , and  136  are located within cell  102 , mobile devices  142  and  144  are located within cell  104 , mobile devices  152  and  154  are located within cell  106 , and mobile devices  162  and  164  are located within cell  108 . Each of these mobile devices can be a variety of different computing devices capable of wireless communication with a cellular base station. For example, a mobile device can be a cellular phone, a car phone, a personal digital assistant (PDA), a laptop or other portable computer, an automotive PC, and so forth. Additionally, the mobile devices are referred to as being mobile due to their ability to maintain communication with a cellular base station of system  100  as the mobile devices transition from one cell to another. However, such mobile devices need not be moved and can remain stationary in a particular location. 
     The cellular base station in a cell is responsible for handling or managing mobile devices in that cell. The managing of a mobile device refers to the cellular base station coordinating various communications desired by the mobile device. These communications can take a variety of different forms, such as phone calls, email or other messages, Internet or other network data transfers, and so forth. As part of managing a mobile device, the cellular base station receives data from the mobile device and forwards such data to the appropriate destination, and also receives data targeting the mobile device and communicates such data to the mobile device. To facilitate these communications, the managing provided by the cellular base station also includes communicating control information to the mobile device and/or receiving control information from the mobile device. 
     As a mobile device moves within a cell, the cellular base station for that cell maintains responsibility for managing that mobile device. However, when a mobile device moves into a neighboring cell, responsibility for managing that mobile device is transferred to the cellular base station of that neighboring cell. For example, as a mobile device moves within cell  102 , responsibility for managing a mobile device remains with cellular base station  112 . However, if the mobile device were to move into cell  108 , then responsibility for managing the mobile device is transferred to cellular base station  118 . The cellular base stations communicate with one another to coordinate such transfers of responsibility. 
     Although cells are not illustrated as overlapping in  FIG. 1 , it is to be appreciated that different cells in cellular communications system  100  can overlap one another. The cellular base stations responsible for managing mobile devices within overlapping cells communicate with one another and determine, in accordance with the protocol implemented by cellular communications system  100 , which of the cellular base stations is responsible for managing the mobile device in an area that is overlapped by multiple cells. 
     Cellular base stations can support a variety of different protocols and/or techniques to allow such requests and other information to be communicated among the cellular base stations. In one or more embodiments, requests and other information can be communicated among the cellular base stations via an X2 link protocol supported by cellular base stations using the 3GPP LTE (3 rd  Generation Partnership Project Long Term Evolution) standard. 
     Each mobile device in a cell communicates with the cellular base station for that cell. This communication includes the mobile device sending signals to the cellular base station (also referred to as an uplink), as well as receiving signals from the cellular base station (also referred to as a downlink). Although a particular cellular base station expects to receive signals from mobile devices that the cellular base station is responsible for managing, situations can arise in which a cellular base station also receives signals from other mobile devices in other cells that the cellular base station is not responsible for managing. Signals received by a cellular base station from a mobile device that the cellular base station is not responsible for managing are also referred to as interference for the cellular base station as such signals can interfere with the signals received from mobile devices that the cellular base station is responsible for managing. For example, cellular base station  112  is responsible for managing mobile devices  132 ,  134 , and  136 . However, cellular base station  112  can also receive signals sent by other mobile devices, such as mobile device  142  and  154 . Signals that cellular base station  112  receives from mobile devices  142  and  154  are referred to as interference (from the perspective of cellular base station  112 , mobile device  136 , and cell  102 ). 
     A cellular base station employs an interference detection technique to detect which other surrounding cell(s) include mobile devices that are causing interference to a mobile device managed by the cellular base station. For example, if cellular base station  112  detects that signals received from mobile device  136  are being interfered with by a threshold amount, then cellular base station  112  detects which other cell  104 ,  106 , or  108  includes one or more mobile devices that are generating this interference. 
       FIG. 1  illustrates cellular base station  112  in additional detail. Only one cellular base station is shown in additional detail in  FIG. 1  in order to avoid cluttering the drawings, although it is to be appreciated that the other cellular base stations  114 ,  116 , and  118  are analogous to cellular base station  112 . Cellular base station  112  includes a communicator  172 , an interference analyzer  174 , and a locator  176 . Communicator  172 , interference analyzer  174 , and locator  176  can be implemented in software, firmware, hardware, or combinations thereof. 
     Communicator  172  manages communications with mobile devices in cell  102  as well as communications with cellular base stations in other cells. Communicator  172  manages receiving signals from mobile devices in cell  102 , sending signals to mobile devices in cell  102 , receiving requests from cellular base stations in other cells, sending requests to cellular base stations in other cells, and so forth. 
     During operation, communicator  172  generates measurements of interference in the signals received from each of the mobile devices in cell  102 . In one or more embodiments, these measurements of interference are signal-to-noise ratio (SNR) measurements, each of which is a measure of the power of the intended signal from a mobile device relative to interference with that intended signal when the signal is received. The signal-to-noise ratio measurements can be generated using conventional techniques, and are used by communicator  172  in managing the mobile devices in cell  102 . Additionally, the signal-to-noise ratio measurements (or other measures of interference generated by communicator  172 ) are leveraged by the location-based detection of interference in cellular communications systems and used to reduce interference in certain situations as discussed in more detail below. 
     Interference analyzer  174  obtains the measurements of interference (e.g., signal-to-noise ratio measurements) generated by communicator  172  for the mobile devices in cell  102  and analyzes these obtained measurements. In one embodiment, analyzer  174  analyzes these obtained measurements of interference and determines when the interference for a particular mobile device exceeds a threshold amount. The interference can be determined to exceed the threshold amount when, for example, the interference exceeds a particular value for a particular amount of time. 
     In situations when interference analyzer  174  determines that the interference for a particular mobile device exceeds the threshold amount, locator  176  determines the neighboring cell that is responsible for the interference. The neighboring cell that is responsible for the interference is the neighboring cell that includes one or more mobile devices that are sending signals that are causing interference. This neighboring cell is determined based at least in part on the location of the particular mobile device for which measurements of interference exceeds a threshold amount, as discussed in more detail below. 
     With the neighboring cell that is responsible for the interference having been determined, communicator  172  sends a request to the cellular base station responsible for managing mobile devices in that neighboring cell. This request is a request for the cellular base station responsible for managing devices in that neighboring cell to take action to reduce the interference being generated by the devices in that neighboring cell. 
     In addition to communicator  172 , interference analyzer  174 , and locator  176 , cellular base station  112  can include various additional well-known components and/or modules. These additional components and/or modules provide various functionality for cellular base station  112  in managing mobile devices in cell  102 . These additional components and/or modules, however, have not been shown in  FIG. 1  in order to avoid cluttering the drawings. 
       FIG. 2  is a flowchart illustrating an example process  200  for implementing the location-based detection of interference in cellular communications systems in accordance with one or more embodiments. Aspects of process  200  may be implemented in hardware, firmware, software, or a combination thereof. Process  200  is described in the form of a set of blocks that specify operations to be performed, and the operations are not necessarily limited to the order shown. The operations performed by the set of blocks in process  200  are performed by a cellular base station, such as a cellular base station  112 ,  114 ,  116 , or  118  of  FIG. 1 . Process  200  is discussed with additional reference to  FIG. 1 . 
     At block  202  an interference analyzer (such as interference analyzer  174  of  FIG. 1 ) analyzes signals received from a mobile device. The analysis in block  202  is an analysis of the measurements of interference (e.g., the signal-to-noise ratio measurements) obtained from a communicator (such as communicator  172  of  FIG. 1 ). In one or more embodiments, the analysis in block  202  is performed for each mobile device that the cellular base station implementing process  200  is responsible for managing, although alternatively the analysis in block  202  may not be performed for certain mobile devices. 
     The analysis in block  202  determines whether the interference for the mobile device exceeds a threshold amount. In one or more embodiments, the analysis in block  202  includes determining if the measurements of interference for the mobile device obtained from the communicator indicate that the interference exceeds a particular value for a particular amount of time. This particular amount of time can vary, for example, by being dependent on how much the interference exceeds the particular value and/or whether interference for other mobile devices also exceeds the particular value. For example, if the interference exceeds the particular value by greater than a certain percentage or certain amount, then the particular amount of time can be reduced. By way of another example, if multiple other mobile devices (optionally other mobile devices within a threshold distance of the mobile device) also have measurements of interference that exceed the particular value, then the particular amount of time can be reduced. 
     Based on the analysis in block  202 , at block  204  the interference analyzer determines when a neighboring cell is generating interference for a mobile device that exceeds the threshold amount. The interference analyzer makes this determination in one or more of a variety of different manners. In one or more embodiments, the interference analyzer determines that a neighboring cell is generating interference for a mobile device that exceeds a threshold amount when the interference analyzer determines in block  202  that the measurements of interference obtained from the communicator for the mobile device exceed a particular value for a particular amount of time. This particular amount of time is identified in one or more of a variety of different manners, such as a particular number of consecutive interference measurements exceeding the particular value, or a particular percentage (e.g., one-half or two-thirds) of a particular number of consecutive interference measurements exceeding the particular value. 
     At block  206 , a locator (such as locator  176  of  FIG. 1 ) identifies the particular neighboring cell that is generating the interference. The locator identifies the neighboring cell that is generating the interference based on the location of the mobile device for which the interference exceeding the threshold amount was determined to have been generated. In one or more embodiments, the locator identifies the neighboring cell that is closest to the mobile device for which the interference has been determined to exceed a threshold amount as the neighboring cell that is generating the interference. The locator identifies this neighboring cell that is closest to the mobile device in one or more of a variety of different manners. Typically, the locator is aware of the location of each mobile device in cell  102  that cellular base station  112  is responsible for managing. The locator identifies the particular location of a mobile device in cell  102  in one or more of a variety of different manners, such as by tracking (e.g., triangulating on) the signals sent by the mobile device, receiving an indication of the location of the device (e.g., global positioning system (GPS) coordinates) from the device, and so forth. The locator can track these locations, or alternatively can access another component or module that tracks or otherwise obtains these locations. 
     Additionally, the locator is aware of the topology of the cells in cellular communications system  100 . This topology refers to the locations of the different cells (and/or cellular base stations) in system  100 . The locator identifies this topology in a variety of different manners, such as by obtaining an indication of the topology from an administrator or developer of system  100 , by obtaining identifications of the locations of the cellular base stations from the cellular base stations, and so forth. 
     Given the location of the mobile device for which the interference has been determined to exceed the threshold amount and the topology of the cells in cellular communications system  100 , the locator readily identifies the neighboring cell that is physically closest to the mobile device for which the interference has been determined to exceed the threshold amount. The locator makes this identification, for example, by identifying the cell (or cellular base station) that is physically closest to the mobile device for which the interference has been determined to exceed the threshold amount. 
     In other embodiments, the locator identifies the neighboring cell that is closest to the mobile device in other manners. For example, the locator can identify the neighboring cell that is closest to the mobile device based on a direction. The locator identifies the location of the mobile device for which the interference has been determined to exceed the threshold amount as discussed above. Additionally, the locator identifies a direction of that mobile device from the cellular base station responsible for managing the device (e.g., cellular base station  112 ). The locator knows the location of the cellular base station, and given the location of the mobile device the locator readily identifies this direction. Based on the topology of the cells in cellular communications system  100  and following a path from the cellular base station to the mobile device and continuing beyond the mobile device, the locator determines that the next cell encountered in that direction is the neighboring cell that is generating the interference. 
     In block  208 , the communicator sends a request to the cellular base station of the neighboring cell identified in block  206  to reduce the interference. In one or more embodiments, the request to reduce interference is also referred to as an overload indicator (OI). In response to the request, the cellular base station receiving the request can attempt to reduce the interference by altering the operation of one or more of the mobile devices it manages in a variety of different conventional manners. For example, the cellular base station can attempt to reduce interference by requesting that one or more mobile devices in the cell managed by the cellular base station reduce their transmitting power, by altering the scheduling of when signals are sent by one or more mobile devices in the cell managed by the cellular base station, and so forth. 
     The cellular base station receiving the request can attempt to reduce interference from all mobile devices in the cell managed by that cellular base station, or alternatively only in particular mobile devices. For example, the cellular base station receiving the request can identify one or more mobile devices in the cell managed by that cellular base station that are close to (e.g., within a particular distance of) a cell managed by the cellular base station from which the request was received. The cellular base station receiving the request readily identifies the mobile devices close to the cell based on the location of those mobile devices as well as the topology of the cells in the cellular communications system and the cellular base station from which the request to reduce interference was received. A cellular base station can attempt to reduce interference from mobile devices that are within a threshold distance of the cell managed by the cellular base station from which the request was received, but not from other mobile devices. For example, if cellular base station  116  receives a request from cellular base station  112  to reduce interference, cellular base station  116  can attempt to reduce interference from mobile device  154  (which can be determined as being close to cell  102 ). However, cellular base station  112  need not attempt to reduce interference from mobile device  152  (e.g., the operation of mobile device  152  can remain unchanged). 
       FIG. 3  is a flowchart illustrating another example process  300  for implementing the location-based detection of interference in cellular communications systems in accordance with one or more embodiments. Aspects of process  300  may be implemented in hardware, firmware, software, or a combination thereof. Process  300  is described in the form of a set of blocks that specify operations to be performed, and the operations are not necessarily limited to the order shown. The operations performed by the set of blocks in process  300  are performed by a cellular base station, such as a cellular base station  112 ,  114 ,  116 , or  118  of  FIG. 1 . Process  300  is discussed with additional reference to  FIG. 1 . 
     In block  302 , a communicator (such as communicator  172  of  FIG. 1 ) measures signal-to-noise ratios of signals received from mobile devices. 
     In block  304 , an interference analyzer (such as interference analyzer  174  of  FIG. 1 ) checks whether the signal-to-noise ratio measurement for a mobile device is less than an interference threshold. It is to be appreciated that higher signal-to-noise ratio measurements indicate less interference than lower signal-to-noise ratio measurements. Accordingly, the signal-to-noise ratio being less than an interference threshold indicates that the interference exceeds a threshold amount. 
     The interference threshold is one or more of a variety of different values that are established in a variety of different manners that vary by implementation. In one or more embodiments, a particular interference threshold is established by weighing the desire to detect interference from one or more mobile devices of one or more neighboring cells against the desire to avoid false positives (e.g., avoiding identifying interference from another source as being interference from or more mobile devices of one or more neighboring cells). For example, the interference threshold can be determined empirically based on administrators or other users or devices analyzing the operation of the cellular base stations and signals received from the mobile devices. 
     Additionally, in one or more embodiments the interference analyzer determines that the signal-to-noise ratio is less than the interference threshold  304  based on multiple measurements of signals received from a mobile device. The frequency with which signal-to-noise ratio measurements are made can vary based on the technology and/or protocol implemented by the cellular base station. For example, the signal-to-noise ratio measurements can be made 15 times every 10 milliseconds (ms). In order for the signal-to-noise ratio measurements to be less than the interference threshold, the signal-to-noise ratio measurements are to indicate that the interference exceeds a particular value for a particular amount of time. The signal-to-noise ratio measurements can indicate that the interference exceeds a particular value by the signal-to-noise ratio measurements being less than a particular value. This particular amount of time can be, for example, a particular number of consecutive measurements that are to be less than the particular value, at least a particular percentage of consecutive measurements are to be less than the particular value, and so forth. For example, this particular amount of time can indicate that five consecutive signal-to-noise ratio measurements are to be less than the particular value. By way of another example, this particular amount of time can indicate that one-half or two-thirds of any 15 consecutive signal-to-noise ratio measurements are to be less than the particular value. This particular amount of time can also vary as discussed above, such as being dependent on how much the signal-to-noise ratio measurements are below the particular value and/or whether signal-to-noise ratio measurements for other mobile devices are less than the interference threshold. 
     The interference analyzer checks the signal-to-noise ratio measurements of signals received from the mobile devices until the signal-to-noise ratio measurements for a mobile device are less than the interference threshold. In block  306 , when the interference analyzer determines that the signal-to-noise ratio measurements from a mobile device are less than the interference threshold, then a locator (such as locator  176  of  FIG. 1 ) performs a direction-finding process. The direction-finding process identifies a direction, relative to the cellular base station implementing process  300 , where the mobile device for which the signal-to-noise ratio measurements were determined to be less than the interference threshold in block  304  is located. This direction is determined based on the location of the cellular base station and the mobile device as discussed above. 
     The direction-finding process continues until the direction is found. In block  310 , the locator identifies the neighboring cell responsible for the interference based on the direction found in block  308  and the cell topology. This neighboring cell is the neighboring cell closest to the mobile device for which the signal-to-noise ratio measurements were determined to be less than the interference threshold in block  304 . In block  312 , this identification process continues until the locator identifies the neighboring cell responsible for the interference. After the locator identifies the neighboring cell, in block  314  the communicator sends a request to reduce interference to the neighboring cell. The neighboring cell can then act to attempt to reduce the interference in a variety of different manners as discussed above. 
     Process  300  is discussed above using a direction-based technique in blocks  306 - 312 . Alternatively, other techniques can be used to identify the neighboring cell, such as the cell that is closest to the mobile device for which the signal-to-noise ratio measurements were determined to be less than the interference threshold in block  304  as discussed above. 
     As can be seen from the discussions herein, the location-based detection of interference in cellular communications systems leverages signals and measurements already being used by the cellular base stations. For example, signal-to-noise ratio measurements that are already being measured by the cellular base stations for other uses can be leveraged for the location-based detection of interference in cellular communications systems. Accordingly, no additional signals need be sent by the mobile devices in order to detect the interference. Rather, the signals otherwise used by the cellular base stations and mobile devices to communicate data and/or control information between one another are leveraged by the location-based detection of interference in cellular communications systems. Additionally, no special actions need be taken by the mobile devices in order to detect the interference, such as no coordinated periods of silence need be performed by the mobile devices in order to detect the interference. 
     Additionally, as can be seen from the discussions herein the detection of interference in cellular communications systems is location-based. When a cellular base station detects that signals from a mobile device are being interfered with by a threshold amount, the cellular base station identifies the neighboring cell responsible for the interference based on the location of that mobile device. The cellular base station also requests that the cellular base station responsible for managing mobile devices in that neighboring cell attempt to reduce the interference. A broadcast statement to all neighboring cells need not be made; rather, the request can be sent just to the neighboring cell responsible for the interference. Accordingly, other neighboring cells need not attempt to reduce interference generated by mobile devices in those cells. 
       FIG. 4  is a generalized example of a computing device  400  that can be used to implement the location-based detection of interference in cellular communications systems in accordance with one or more embodiments. Computing device  400  can implement, for example, a cellular base station of  FIG. 1  or portion thereof. For example, computing device  400  can implement communicator  172 , interference analyzer  174 , and locator  176  of  FIG. 1 . Computing device  400  can also implement, for example, a mobile device of  FIG. 1 . 
     One or more processing units, such as a central processing unit (CPU)  402 , are included in computing device  400 . A memory system  404  including a memory controller  406 , random access memory (RAM) memory storage  410  and read only memory (ROM) memory storage  412  can store instructions and data for execution and use by CPU  402 . Suitable bus architectures include a system bus  408 , as well as a memory bus for communication between the CPU and memory system  404  via memory controller  406 , and a peripheral bus for communication with peripheral devices. Additional hardware including mass data storage (e.g., a hard disk drive (HDD)  416 ) and an optical drive  418  (e.g., a digital video disk (DVD) drive) may be coupled to the CPU through respective drive interfaces. Input/output devices such as displays  420 , keyboards  422 , touchscreens  424 , and so forth may be coupled via a video adapter in the former case and various serial or parallel interfaces  426  in the latter two cases. Example input/output interfaces include serial ports, parallel ports, universal serial buses (USB), video adapters, etc. Other hardware can be included in a similar fashion. One or more transceivers  428  can be included for communicating with other devices via one or more cellular network(s)  430 . 
     Although the subject matter has been described in language specific to structural features and/or methodological operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above, including orders in which they are performed.