Abstract:
Systems and methods of extending base station coverage are provided. Idle mode mobile stations supported by a base station are identified, and at least one of the idle mode mobile stations is selected based on a location of the at least one idle mode mobile station. A communication with an active mode mobile station that is associated with the at least one idle mode mobile station is established. The active mode mobile station is not able to directly receive communications from the base station, and the identification and selection of idle mode mobile stations and the establishment of the communication are performed by the base station.

Description:
BACKGROUND OF THE INVENTION 
     Wireless macro communication networks are typically composed of a number of base stations, each base station including a coverage area commonly referred to as a cell. The size of the coverage area of a cell is influenced by a number of factors, including transmission power, pathloss, interference, and/or the like. Base stations are typically arranged such that the coverage areas of adjacent cells have a small area of overlap, which allows for handover from one base station to the next. 
     SUMMARY OF THE INVENTION 
     Although cells theoretically have a uniform coverage area, in practice the coverage area may be larger in some parts of a cell than others. Thus, due to interference and/or obstructions, portions of a cell may not actually overlap with portions of an adjacent cell. Moreover, base station placement depends upon a number of factors, including allocation of frequencies by government bodies, the ability to acquire a location for the base station and/or zoning regulations. Accordingly, wireless communication networks can include areas that do not have sufficient coverage provided by base stations. 
     Systems and methods of extending base station coverage are provided. Idle mode mobile stations supported by a base station are identified, and at least one of the idle mode mobile stations is selected based on a location of the at least one idle mode mobile station. A communication with an active mode mobile station that is associated with the at least one idle mode mobile station is established. The active mode mobile station is not able to directly receive communications from the base station, and the identification and selection of idle mode mobile stations and the establishment of the communication are performed by the base station. 
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
         FIG. 1  is a block diagram of an exemplary system in accordance with the present invention; 
         FIG. 2A  is a block diagram of an exemplary base station in accordance with the present invention; 
         FIG. 2B  is a block diagram of an exemplary idle mode mobile station in accordance with the present invention; and 
         FIG. 3  is a flow diagram of an exemplary method in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a block diagram of an exemplary system in accordance with the present invention. The system includes base station  102 , idle mode mobile stations  104   1  and  104   2 , and active mode mobile stations  106   1  and  106   2 . Base station  102  provides a coverage area  110 , idle mode mobile station  104   1  provides coverage area  115  and idle mode mobile station  104   2  provides coverage area  120 . In accordance with exemplary embodiments of the present invention, base station  102  selects one or more idle mode mobile stations to extend the base station&#39;s coverage area in order to support communications with active mode mobile stations located outside of the base station&#39;s coverage area. In  FIG. 1 , active mode mobile station  106   2  is located outside of coverage area  110  of base station  102 , however, base station  102  employs idle mode mobile station  104   1  as a repeater to provide communications between base station  102  and active mode mobile station  106   2 . 
     Although the system of  FIG. 1  illustrates two idle mode mobile stations and two active mode mobile stations, the present invention is equally applicable to systems that include more or less of either of these types of mobile stations. Furthermore, coverage areas  110 ,  115  and  120  are nearly exemplary, and these coverage areas can be different sizes and/or shapes from that illustrated in  FIG. 1 . 
       FIG. 2A  is a block diagram of an exemplary base station in accordance with the present invention. Base station  102  includes processor  206  coupled between memory  204  and transceivers  202   1  and  202   2 . Transceivers  202   1  and  202   2  are each respectively coupled to an antenna. Processor  206  includes logic  208  through  218 , which will be described in more detail below in connection with  FIG. 3 . Processor  206  can be any type of processor, such as a field programmable gate array (FPGA), application specific integrated circuit (ASIC), and/or a microprocessor. When processor  206  is a microprocessor, logic  208  through  218  can be computer executable instructions that are loaded from a computer readable medium, such as memory  204 . Memory  204  can be any type of memory, including random access memory (RAM), read only memory (ROM), flash memory, a hard disk, a CD, a DVD, and/or the like. 
       FIG. 2B  is a block diagram of an exemplary idle mode mobile station in accordance with the present invention. Mobile station  104   n  includes a processor  256  coupled to memory  254 . Processor  256  and memory  254  can be any type of processor and memory, such as those discussed above in connection with base station  102 . Processor  256  is coupled to transceiver  252   1  via downconverter/upconverter  256 , in order to exchange communications with a base station that originate from, or are destined to, an active mode mobile station located outside of the base station&#39;s coverage area. Transceiver  252   2  is coupled to downconverter/upconverter  256  in order to repeat communications between a base station and an active mode mobile station. Although not illustrated, mobile station  104   n  can include additional elements, such as a power amplifier for amplifying communications transmitted by the mobile station either to the base station or to an active mode mobile station. 
       FIG. 3  is a flow diagram of an exemplary method in accordance with the present invention. Initially, logic  208  of base station  102  identifies idle mode mobile stations, such as idle mode mobile stations  104   1  and  104   2  (step  305 ). Logic  210  then determines the location of the identified idle mode mobile stations (step  310 ). The location of the idle mode mobile stations can be identified in any number of ways, such as based on Global Positioning Satellite (GPS) information, the sector in which the idle mode mobile station is located, and/or using pathloss and/or transmission power values to determine the distance of the idle mode mobile station from the base station. 
     Logic  212  selects a subset of the idle mode mobile stations based upon location (step  315 ), and logic  214  transmits broadcast messages to the selected idle mode mobile stations (step  320 ). Specifically, in order to reduce interference, the base station does not employ all idle mode mobile stations as repeaters. Thus, if a number of idle mode mobile stations are situated within a similar location, only one or two of the mobile stations may be selected by the base station. Moreover, as will be described below, the base station identifies the location of active mode mobile stations that are located outside of the base station&#39;s coverage area. Accordingly, after such active mode mobile stations are identified and the process returns to step  305 , the subset of idle mode mobile stations can include those idle mode mobile stations located in proximity to the active mode mobile station. The broadcast messages can be any type of conventional broadcast messages, such as messages used for identifying a base station to allow a mobile station to register with the base station. The broadcast messages are received by mobile station  104   n  via transceiver  252   2  and rebroadcast such that an active mode mobile station located outside of the base station&#39;s coverage area can exchange communications with the base station. 
     Logic  216  determines whether the base station has received any registration responses from idle mode mobile stations (step  325 ). These registration response messages can be received by the base station via one of the selected idle mode mobile stations. When logic  216  determines that registration responses have been received (“Yes” path out of decision step  325 ), then logic  216  examines the response message in order to store the location of the active mode mobile station that originally sent the registration response message (step  330 ). The registration response message will include some type of location information, such as GPS information. If a registration response has not been received (“No” path out of decision step  325 ), or after storing the location of the active mode mobile station from a received registration response (step  330 ), then logic  218  determines whether the base station has received a call request for a remote mobile station (step  335 ). The call request can originate from a mobile station located within the cell of the base station, or can be received from the infrastructure network from another mobile station or a landline station. 
     When logic  218  determines that a call request is received (“Yes” path out of decision step  335 ), then logic  218  identifies an idle mode mobile station in proximity of the active mode mobile station to which the call request is intended as an associated mobile station, forwards the call request to the idle mode mobile station associated with the remote station and uses the associated idle mode mobile station to support a call between base station  102  and the remote mobile station (steps  340  and  345 ). Specifically, referring now to  FIG. 2B , the call request will be forwarded to mobile station  104   n , which will be received by transceiver  252   2 , downconverted and upconverted by downconverter/upconverter  256 , and amplified (if necessary) prior to transmission to the remote active mode mobile station, and communications between the active mode mobile station and the base station will follow similar processing. 
     When, however, a call request for a remote mobile station has not been received (“No” path out of decision step  335 ), then logic  218  determines whether it has received a call request from a remote mobile station associated with an idle mode mobile station (step  350 ). Idle mode mobile station  104   n  will receive the call request from the active mode mobile station by transceiver  252   2 , downconvert and upconvert the received request using downconverter/upconverter  256 , amplify the request (if necessary) and transmit the call request to base station  102  using transceiver  252   2 . 
     When base station  102  receives a call request from a remote mobile station via an idle mode mobile station (“Yes” path out of decision step  350 ), then logic  218  identifies an idle mode mobile station in proximity of the active mode mobile station to which the call request originated as an associated mobile station and uses the associated idle mode mobile station to support a call with the remote mobile station (step  355 ). It should be recognized that the idle mode mobile station that forwarded the call request may not necessarily be the one that is identified as the associated mobile station. When a call request is not received from a remote mobile station (“No” path out of decision step  350 ) or after steps  345  and  355 , processing returns to step  305  in order to identify idle mode mobile stations. 
     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.