Abstract:
A code division multiple access telecommunications network including an underlay base station in a private premises and a plurality of overlay macro base stations. The underlay base station includes a GPS receiver and a mobile unit receiver. The underlay base station uses its geographic location to obtain information identifying macro base stations within a preselected distance of the underlay base station. It uses the mobile receiver to measure pilot signal strength of the macro base stations. It generates a neighbor list of the identified macro base stations ranked according to pilot signal strength.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    None 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       REFERENCE TO A MICROFICHE APPENDIX 
       [0003]    Not applicable. 
       BACKGROUND 
       [0004]    The present disclosure relates to cellular networks and more particularly to code division multiple access, CDMA, base stations which support self configuration of neighbor lists to enable handoff of mobile units between base stations. 
         [0005]    Inadequate coverage is a persistent problem in the quality of service of any wireless network. Natural and man-made obstacles frequently create radio frequency (RF) holes, i.e. areas of low or no RF signal, in the coverage area of a wireless network. Voice and data call connections are frequently dropped when a wireless terminal, such as a cell phone or a similar mobile station, enters an RF hole. Typical areas in which RF holes occur include homes, apartments, underground tunnels and office buildings. 
         [0006]    Conventional public CDMA cellular systems include a number of macro base stations arranged to provide service in contiguous cells. As mobile units move between cells, the mobile units are handed off between macro base stations to maintain continuous service. Each macro base station, MBS, maintains a neighbor list, comprising information identifying the MBSs for all contiguous cells. The neighbor list is communicated to the mobile units to enable handoff as the mobile units move into new cells. When a new MBS is installed, its neighbor list is manually generated by technicians based on the known location of the new MBS and locations of surrounding MBSs. Various RF measurements may be taken by the technicians to verify the power levels of nearby MBSs for the neighbor list. The manual generation of the neighbor list is expensive in terms of labor hours and equipment utilized, but is a small part of the overall cost of installing a MBS. 
       SUMMARY 
       [0007]    In a CDMA telecommunication network, an underlay base station includes a GPS receiver providing geographic location of the underlay base station. The underlay base station transmits the location information to a server having a database of macro base stations in the network. The server returns a list of identifying information for macro stations within a preselected distance of the underlay base station. The macro station information is recorded as a neighbor list for the underlay base station. 
         [0008]    In an embodiment, the underlay base station includes a mobile unit receiver. The receiver is operated to receive and measure the strength of beacon pilot signals from the identified macro base stations. The macro base stations on the neighbor list are ranked according to beacon signal strength. 
         [0009]    The neighbor list is provided to mobile units served by the underlay base station to facilitate hand off of the mobile units from the underlay base station to the macro base stations. 
         [0010]    These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    For a more complete understanding of the present disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts. 
           [0012]      FIG. 1  is a general diagram of a CDMA cellular system overlaying a home base station. 
           [0013]      FIG. 2  is a block diagram of a home base station. 
           [0014]      FIG. 3  is a flow diagram of a method of one embodiment. 
           [0015]      FIG. 4  illustrates an exemplary general purpose computer system suitable for implementing the several embodiments of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    It should be understood at the outset that although illustrative implementations of one or more embodiments are illustrated below, the disclosed systems and methods may be implemented using any number of techniques, whether currently known or in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, but may be modified within the scope of the appended claims along with their full scope of equivalents. 
         [0017]    A “home base station” (HBS) can be used to fill an RF hole in a home for the home mobile devices, or mobile stations. HBSs are intended to serve only a small area, for example one private residence or business office, and a small number of wireless devices, e.g. mobile units. The number of HBSs is therefore expected to be much larger than the number of MBSs. Each HBS needs to have a neighbor list, just like a MBS, to enable handoff of mobile units from the HBS to a MBS when the mobile units move away from the HBS, e.g. move outside a private residence or other premises served by the HBS. For HBSs to be a commercial success, the cost of equipment and labor should be kept to a minimum. 
         [0018]      FIG. 1  illustrates a CDMA cellular system  10  configured according to an embodiment. The system  10  includes a large number of macro base stations, MBSs, of which two MBSs  12  and  14  are shown in  FIG. 1 . MBS  12  serves a cell indicated by the circle  16  and MBS  14  serves a contiguous cell indicated by the circle  18 . A private residence  20  is located within the cell  18 . Within the residence  20  is located a home base station, HBS,  22 . The HBS serves a small cell including the area enclosed by the residence  20  and possibly a small area immediately surrounding the residence  20  as indicated by the circle  24 . A mobile unit, MU,  26  is shown within the residence  20  and therefore within the cell  24  and is served by the HBS  22 . A second MU  28  is shown within the cell area  18 , but outside the residence  20 , and is served by the MBS  14 . In this configuration, the cell  24  is considered an underlay cell relative to the cell  18  and the cell  18  is considered an overlay cell relative to the cell  24 . The cell  16  and other cells may also be considered to be overlay cells relative to cell  24 , depending on distance and signal strength as discussed below. 
         [0019]    Mobile units  26  and  28  may be any suitable wireless devices (e.g., conventional cell phones, PCS handsets, personal digital assistant (PDA) handsets, portable computers, telemetry devices, etc.) that are capable of communicating with base stations  12 ,  14 ,  22  via wireless links. It should be understood that the use of the term “mobile unit” in the claims and in the description below is intended to encompass both truly mobile devices (e.g., cell phones, wireless laptops) and stationary wireless terminals (e.g., a machine monitor with wireless capability). 
         [0020]      FIG. 2  illustrates more details of an embodiment of a HBS  22 . The HBS  22  includes all the functional elements of a conventional CDMA base station, such as those used in MBSs  12  and  14 . The HBS  22  includes an antenna  30  for communicating with mobile units. HBS  22  includes a global positioning satellite, GPS, receiver  32  for receiving position and timing information. In addition, HBS  22  includes a mobile module, or over the air receiver,  34  which provides the functionality of a mobile unit, such as MUs  26  and  28 . 
         [0021]    The HBS  22  has a connection  36  to a network  38 , e.g. the Internet. The connection  36  may be through an ISP (Internet Service Provider) used by the occupants of the residence  20 . The connection  36  may be any conventional IP (Internet Protocol) or other connection, but preferably is a high speed connection such as cable, DSL (digital subscriber line) or an optical fiber system. The HBS  22  connects through the connection  36  to a server  40  operated by the cellular telephone service provider. In this embodiment, the server  40  also stores information identifying the MBSs operated by the cellular telephone service provider, including MBSs  12  and  14 . 
         [0022]    The disclosed embodiments operate with conventional mobile units, i.e. no modifications are required for MU  26  or  28  to be provided service by the HBS  22 . The HBS  22  may provide all or most of the functions normally provided by a MBS. One of those functions is providing a neighbor list to each MU which it serves. The neighbor list information is needed by the MU to enable hand over or hand off to a MBS, e.g. MBS  14  or  16 , when a MU is moved from the cell  24 . The HBS  22  of this embodiment is intended to be a private system serving private premises with a small number of mobile units. It is desirable that the cost of equipment and installation services be kept as low as possible. The disclosed embodiments provide an HBS  22  which may automatically and autonomously configure a neighbor list without manual intervention or assistance by a technician or by an occupant of the residence  20 , which may result in reduced cost. 
         [0023]    Operation of the disclosed embodiments will be described with reference to the flow chart of  FIG. 3 . At step  50 , the HBS  22  is started, e.g. the system is installed and power is turned on. The startup step may be repeated whenever power is restored to HBS after a power outage or upon another restart event, e.g. manual activation of a reset or restart button or receipt of a restart command from a remote server. The HBS  22  may be programmed to automatically restart or recheck or audit on a daily basis or more often to ensure that the neighbor list is up to date. 
         [0024]    At step  52 , the HBS  22  uses the GPS unit  32  to determine the location, i.e. latitude and longitude of the HBS  22 . At step  54 , the HBS  22  transmits the GPS location information to the server  40 . The server  40  is operated by the telephone service provider which may have provided the HBS  22  to an end user, e.g. an occupant of the residence  20 . The server  40  stores information identifying all MBSs in the service providers cellular network. The server  40  determines which MBSs are within a preselected distance, e.g. five or ten kilometers, from the location of the HBS  22 . In one embodiment, the preselected distance may be set to a default value of one hundred kilometers. The server  40  then sends the identifying information for the MBSs back to the HBS  22  at step  56 . The identifying information, for example, includes the distance to each MBS, the switch ID of the mobile switching center serving each MBS, the RF channel and PN (pseudonoise) codes for each MBS, and other information. 
         [0025]    At step  58 , the HBS  22  activates its mobile, or over the air receiver, function  34  so that it may operate like a MU. At step  60 , the HBS  22  uses the mobile function  34  to receive and measure the pilot signal strength from each of the MBSs which were identified by the server  40 . It would be expected that the closest MBS would have the strongest signal. For example, in  FIG. 1 , MBS  14  is illustrated as the closest MBS and would be expected to have a stronger signal at HBS  22 . However, that is often not the case. Due to various topography features, the signal from MBS  12  or another MBS may be stronger at the HBS  22 . The use of the mobile function  34  allows each of the MBSs identified by server  40  to be ranked in the order of the strongest signal to the weakest. 
         [0026]    CDMA MBSs have an average operating range of about five kilometers, i.e. cells have a radius of about five kilometers. However, under some circumstances a MBS may provide good signal strength at a distance of ten kilometers or more. It is therefore desirable to program the server  40  to identify all MBSs within at least five kilometers of the location of the HBS  22  and may be desirable to identify all MBSs within ten kilometers or more. Regardless of which range has been selected, it is possible that at step  60 , the HBS  22  mobile function will not be able to receive and measure the power of pilot signals from all the identified MBSs. Depending on where the HBS  22  is installed within the residence  20 , signals from outside the residence  20  may be greatly attenuated. The attenuation of cellular signals by structural walls is one of the main reasons for RF holes in residences. 
         [0027]    At step  62 , the HBS  22  produces a ranked neighbor list. The list includes identifying information for all of the MBSs which were identified by the server  40 . The MBS which had the highest pilot strength at step  60  will be ranked first. The remaining MBSs will be ranked in descending order of pilot signal strength. For those identified MBSs whose pilot signals could not be detected or measured, the MBSs may be ranked at the bottom of the list in any order, but preferable in the order of increasing distance from the HBS  22 . 
         [0028]    At step  64 , the HBS  22  deactivates the mobile function  34  and operates as a conventional base station. Deactivation of the mobile function  34  may also occur immediately after step  60  or at the same time as step  62 . The HBS provides its own pilot signal and broadcasts its neighbor list to the MUs which it serves, for example MU  26 . The HBS is preferably operated at a power level which does not interfere with MUs outside the private cell  24 , e.g. the MU  28 . If the MU  26  is moved outside the residence  20 , HBS  22  should provide sufficient signal strength within the cell  24  which may extend into the lawn areas surrounding the residence  20 . If the MU  26  is moved outside the cell  24 , the MU  26  should detect a decrease in pilot strength from HBS  22  and an increase in pilot strength from MBS  14 , which should trigger a handoff from HBS  22  to MBS  14  following conventional hand off processes. 
         [0029]    In some circumstances, when MU  26  moves out of cell  24  the MU  26  may find that the pilot strength from MBS  12 , or some other cell, is stronger than the pilot strength from MBS  14 . For example, MBS  14  may be serving its maximum numbers of MUs and may have reduced it output power to shift load to other cells. MBS  12  may be the second ranked MBS in the neighbor list and would be checked by the MU  26  for service after MBS  14 . One purpose of ranking the neighbor list as discussed herein is to increase the percentage of successful handoffs by directing the MUs to the MBSs most likely to have good signal strength. 
         [0030]    While the disclosed embodiments are directed to a base station in a private residence, it is apparent that the present disclosure is equally applicable to other embodiments. The HBS  22  may be used in other locations such as business premises, schools, libraries, etc. Any enclosed structure is likely to generate an RF hole with poor service from the MBSs and service may be improved by installation of an HBS in the structure. Self configuration of a neighbor list in the public MBSs would also reduce the cost of installing and operating such public MBSs. 
         [0031]    The system described above may be implemented on any general-purpose computer with sufficient processing power, memory resources, and network throughput capability to handle the necessary workload placed upon it.  FIG. 4  illustrates a typical, general-purpose computer system suitable for implementing one or more embodiments disclosed herein. The computer system  380  includes a processor  382  (which may be referred to as a central processor unit or CPU) that is in communication with memory devices including secondary storage  384 , read only memory (ROM)  386 , random access memory (RAM)  388 , input/output (I/O)  390  devices, and network connectivity devices  392 . The processor may be implemented as one or more CPU chips. 
         [0032]    The secondary storage  384  is typically comprised of one or more disk drives or tape drives and is used for non-volatile storage of data and as an over-flow data storage device if RAM  388  is not large enough to hold all working data. Secondary storage  384  may be used to store programs which are loaded into RAM  388  when such programs are selected for execution. The ROM  386  is used to store instructions and perhaps data which are read during program execution. ROM  386  is a non-volatile memory device which typically has a small memory capacity relative to the larger memory capacity of secondary storage. The RAM  388  is used to store volatile data and perhaps to store instructions. Access to both ROM  386  and RAM  388  is typically faster than to secondary storage  384 . 
         [0033]    I/O  390  devices may include printers, video monitors, liquid crystal displays (LCDs), touch screen displays, keyboards, keypads, switches, dials, mice, track balls, voice recognizers, card readers, paper tape readers, or other well-known input devices. 
         [0034]    The network connectivity devices  392  may take the form of modems, modem banks, ethernet cards, universal serial bus (USB) interface cards, serial interfaces, token ring cards, fiber distributed data interface (FDDI) cards, wireless local area network (WLAN) cards, and other well-known network devices. These network connectivity  392  devices may enable the processor  382  to communicate with an Internet or one or more intranets. With such a network connection, it is contemplated that the processor  382  might receive information from the network, or might output information to the network in the course of performing the above-described method steps. Such information, which is often represented as a sequence of instructions to be executed using processor  382 , may be received from and outputted to the network, for example, in the form of a computer data signal embodied in a carrier wave 
         [0035]    Such information, which may include data or instructions to be executed using processor  382  for example, may be received from and outputted to the network, for example, in the form of a computer data baseband signal or signal embodied in a carrier wave. The baseband signal or signal embodied in the carrier wave generated by the network connectivity  392  devices may propagate in or on the surface of electrical conductors, in coaxial cables, in waveguides, in optical media, for example optical fiber, or in the air or free space. The information contained in the baseband signal or signal embedded in the carrier wave may be ordered according to different sequences, as may be desirable for either processing or generating the information or transmitting or receiving the information. The baseband signal or signal embedded in the carrier wave, or other types of signals currently used or hereafter developed, referred to herein as the transmission medium, may be generated according to several methods well known to one skilled in the art. 
         [0036]    The processor  382  executes instructions, codes, computer programs, scripts which it accesses from hard disk, floppy disk, optical disk (these various disk based systems may all be considered secondary storage  384 ), ROM  386 , RAM  388 , or the network connectivity devices  392 . 
         [0037]    While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods may be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted or not implemented. 
         [0038]    Also, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component, whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.