WO2012044372A1

WO2012044372A1 - Uniform distribution of load in a mobile communication system

Info

Publication number: WO2012044372A1
Application number: PCT/US2011/037167
Authority: WO
Inventors: David Comstock
Original assignee: Kyocera Corporation
Priority date: 2010-09-28
Filing date: 2011-05-19
Publication date: 2012-04-05

Abstract

Systems and methods for balancing load in a mobile communication system 500 provide even or uniform distribution of the system load among cells. In a first embodiment, periodic load reports 440, 442, 444, 446, 448, 450 are sent to a first base station 405 by neighboring base stations 410. Upon detection of a load imbalance event 470 by the first base station, updated load reports 480, 490 are exchanged and handovers performed 495 to balance load. Load reports may include the maximum number of resources a base station is willing to accept or the minimum number of resources a base station must offload, which may be based on the load of its neighbors. In a second embodiment, periodic load reports are not sent. Base stations 406 compare their own load with previously received loads of their neighbors. Upon detection of a load imbalance event 360, updated load reports 380, 390 are exchanged between neighboring base stations 406, 411.

Description

UNIFORM DISTRIBUTION OF LOAD

IN A MOBILE COMMUNICATION SYSTEM

FIELD OF THE INVENTION

[0001] The present invention relates generally to mobile communication systems and more specifically relates to dynamic distribution of user equipment devices ("UEs") among the radio coverage cells to achieve a more uniform or even distribution of the resource load among the cells.

BACKGROUND [0002] Mobility Load Balancing ("MLB") is a feature standardized in the 3GPP Radio Access Network ("RAN") working group for the Long Term Evolution ("LTE") project, which is the evolution path for Global System for Mobile Communications ("GSM") / Universal Mobile Telecommunications System ("UMTS"). The objective of MLB is to distribute cell load evenly among cells or to transfer part of the traffic from congested cells. This is done by means of self-optimization of mobility parameters or handover actions. A handover action is the procedure performed between neighbor base stations, a user equipment device ("UE"), and, in some cases, other network nodes, in order to change the base station that is providing radio coverage to the UE. Neighbor base stations are base stations that are physically near each other and are adjacent with respect to radio coverage and whose radio coverage usually overlaps. Optimization of mobility parameters is the adjustment of the parameters that determine when a UE should be handed over to a different base station. In many cases, due to the overlap in radio coverage, UEs may be handed over to a neighbor base station for load balancing without changing mobility parameters. In the 3GPP release 9 solution, to facilitate load balancing, LTE base stations (i.e., eNodeBs) request periodic cell load measurement reports from their neighbor LTE base stations and use on-demand procedures (request/response) to request cell load measurement reports from base stations of other types of radio access networks (e.g. UMTS Radio Network Controllers). When a base station's load is too high, it can hand over some of the UEs it is serving to its neighbor cells and may use knowledge of its neighbors' load to determine handover targets. As will be understood by one skilled in the art, the load of a base station may be expressed in terms of the number of its resource blocks being consumed. A base station may select UEs to hand over to a neighbor cell for the purpose of load balancing based on the number of resource blocks they consume as well as the relative strength of the radio signal received by the UEs from the first base station compared to its neighbor.

[0003] The release 9 3GPP solution is inefficient in terms of the amount of signaling required in the network to meet the objectives of the feature. To realize uniform load distribution with periodic and on-demand load reports, base stations must receive load reports from all of their neighbors at all times in order to track load differences. A first base station can only determine that its load is relatively high by receiving load reports from a second base station and then it may perform handovers to correct the situation. A second base station may determine that its load is low relative to a first base station (i.e., a neighbor) by receiving load reports from the first base station, but there is no corrective action that the second base station can take in the prior art solution. To illustrate, a cell with a low load condition cannot trigger its neighbor cells to perform load balancing handovers. Instead, a cell with a lighter load must still continuously receive and send load reports because there is the possibility of a high load condition occurring in the future and it should know its neighbors' load status for consideration during load redistribution actions.

[0004] It is wasteful for both of these neighbor base stations to continuously determine the load difference between them, but it is necessary since there is no means of coordinating this information between them. Therefore, what is needed is a system and method that overcomes these significant problems found in the prior art as described above.

SUMMARY

[0005] In order to solve the previously described problems, event-based triggers are used to allow a base station to send a load report after its load crosses predefined thresholds, rather than only sending a load report at a predetermined rate. In particular, for even/uniform distribution of the load among the cells, the important characteristic is the difference in the load between cells, so that when the load difference between two base stations becomes larger than an allowed margin, the more highly loaded cell hands over some of the user equipment devices ("UEs") it is serving to a neighbor base station. In one embodiment of the current invention, a cell obtains periodic load reports from a neighbor, while the neighbor only receives a load report when the first cell detects a cell load difference that exceeds a predetermined load difference threshold. In this manner, only one of the cells of a neighbor pair receives periodic load reports, which significantly reduces the amount of signaling in the network as compared to the prior art solution. When a cell provides a load report that resulted from such an event-based trigger, the cell includes its current load value and may also include "neighbor load supply" information. The neighbor load supply information is either a Maximum Resource Sink ("MaxSink") parameter, which is sent when the reporting cell has a lower load than its neighbor, or a Minimum Resource Source ("MinSource") parameter, which is sent when the reporting cell has a higher load than its neighbor. MaxSink is the maximum amount of resources a cell will accept from this neighbor and its value may take into consideration the load conditions of its other neighbors. MinSource is the minimum amount of resources a cell needs to offload to this neighbor and its value may take into consideration the load conditions of its other neighbors. [0006] In addition, a cell receiving an event-based load status report sends a response report that includes its load and may also include its neighbor load supply value. This cell has been providing periodic reports to its neighbor, but before receiving the event-based report, this cell had no information about the other cell's load, so the MaxSink/MinSource values can be provided based on the load of this neighbor cell as well as its other neighbor cells. The reporting cell may change its MaxSink/MinSource value based on this information.

[0007] In another embodiment of the invention, each cell of a neighbor pair initially sends a load report including its current load to the other (autonomously or by request) cell, which is stored by the other cell. If the difference between a cell's load and the stored load value for a neighbor ever exceeds the allowed margin, the cell reports its load and the event to the corresponding neighbor. The neighbor responds with its current load and each cell can determine whether a load imbalance actually exists based on the updated load values. [0008] In another embodiment of the invention, absolute load value thresholds are used rather than a load difference threshold. One cell of a neighbor pair requests load reports based on event-based triggers where two absolute cell load value thresholds are provided. One of the thresholds is the requesting cell's load plus the target difference threshold value and the other threshold is the requesting cell's load minus the target threshold difference value. If the reporting cell's load crosses the higher threshold, it will send a load report, and if the imbalance is verified, this cell will perform handovers to correct the imbalance. If the reporting cell reports that it crossed the low threshold, it will send a load report and, if the imbalance is verified, the receiving cell will perform handovers to correct the situation. When the requesting cell's load changes significantly, it can send a new report request with new trigger thresholds. This embodiment further reduces the amount of network signaling required, but there is a loss in the amount of control over the system load distribution since there is less consideration of the changing load of the requesting cell.

[0009] Other features and advantages of the present invention will become more readily apparent to those of ordinary skill in the art after reviewing the following detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The details of the present invention, both as to its structure and operation, may be gleaned in part by study of the accompanying drawings, in which like reference numerals refer to like parts, and in which: [0011] FIG. 1 is a network diagram illustrating an example mobile communication system with uneven distribution of load according to an embodiment of the present invention;

[0012] FIG. 2 is a network diagram illustrating an example mobile communication system with uniform distribution of load according to an embodiment of the present invention;

[0013] FIG. 3 is a block diagram illustrating an example base station in a mobile communication system according to an embodiment of the present invention;

[0014] FIG. 4 is a flow diagram illustrating an example process for balancing resource blocks according to an embodiment of the present invention;

[0015] FIG. 5 is a flow diagram illustrating an example process for balancing resource blocks according to an embodiment of the present invention;

[0016] FIG. 6 is a block diagram illustrating an example pair of base stations balancing resource blocks according to an embodiment of the present invention; [0017] FIG. 7 is a block diagram illustrating an example pair of base stations balancing resource blocks according to an embodiment of the present invention;

[0018] FIG. 8 is a block diagram illustrating an example processor based system that may be used in connection with various embodiments described herein.

DETAILED DESCRIPTION

[0019] Certain embodiments as disclosed herein provide for uniform distribution of load in a mobile communication system. For example, one method as disclosed herein allows for a first base station to receive periodic resource status updates including a load report from a neighbor base station and when the difference between the load of the first base station and the load of the neighbor base station exceeds a predetermined threshold (absolute value or percentage, for example) then the first base station notifies the neighbor base station that a load imbalance event occurred and the more highly loaded base station can hand over user equipment devices ("UEs") to offload the number of resource blocks required to balance the load.

[0020] After reading this description it will become apparent to one skilled in the art how to implement the invention in various alternative embodiments and alternative applications. However, although various embodiments of the present invention will be described herein, it is understood that these embodiments are presented by way of example only, and not limitation. As such, this detailed description of various alternative embodiments should not be construed to limit the scope or breadth of the present invention as set forth in the appended claims. In particular, although the procedures used to describe the various embodiments may be associated with LTE base stations (eNodeBs), the scope of the present invention includes other types of networks, such as load balancing between LTE networks and another type of network (such as a UMTS network) and load balancing for networks other than LTE networks. [0021] FIG. 1 is a network diagram illustrating an example mobile communication system 10 with uneven distribution of load according to an embodiment of the present invention. In the illustrated embodiment, the system 10 comprises a plurality of base stations 20, 30, 40 and 50. The system also comprises a plurality of UEs 60, 62, 64, 66, 68, 70, 72, 74, 76, and 78.

[0022] The plurality of base stations may each be implemented as a variety of processor based devices, an example of which is described in more detail with respect to FIG. 8. Each of the base stations is capable of communicating with other devices over a wired or wireless network medium. For example, the base stations may communicate with each other over a wired communication network (not shown) while simultaneously communicating with UEs over a wireless communication network (also not shown). Additionally, the base stations may communicate with each other using a wireless communication network or a combination of wired and wireless networks.

[0023] The plurality of UEs may each be implemented as a variety of processor based devices, an example of which is described in more detail with respect to FIG. 8. Each of the UEs are capable of communicating over a wireless communication network and may also be capable of communicating over a wired communication network.

[0024] In the illustrated embodiment, base station 20 has a wireless communication range that defines an area surrounding the base station. This area is referred to as cell 25 for base station 20. Similarly, base station 30 has cell 35, base station 40 has cell 45 and base station 50 has cell 55. As shown, the various cells overlap in area and as will be understood by those skilled in the art, the various UEs may change location throughout the system such that they migrate between cells and necessarily communicate with different base stations. As depicted, base station 20 is currently communicating with UEs 60, 62, 70 and 72; base station 40 is currently communicating with UEs 64, 66, 74 and 76; and base station 50 is currently communicating with UEs 68 and 78. As can be seen, base station 30 is currently not communicating with any UE. The system 10 is therefore unbalanced, with more load being handled by base stations 20 and 40. As will be understood by one skilled in the art, the load of a base station may be identified in terms of the number of a base station's resource blocks being consumed. Accordingly, base stations 20 and 40 have more of their resource blocks being consumed in the system 10.

[0025] FIG. 2 is a network diagram illustrating an example mobile communication system 10 with uniform distribution of load according to an embodiment of the present invention. In the illustrated embodiment, the system 10 has balanced its load to the extent that the base station serving UE 62 has changed from base station 20 to base station 30 and the base station serving UE 74 has changed from base station 40 to base station 30. Advantageously, UE 62's serving base station was able to be switched because it was within the radio coverage of both cell 25 and cell 35 and UE 74's serving base station was able to be switched because it was within the radio coverage of both cell 45 and cell 35. As can be seen, the load on base station 50 remained the same.

[0026] To accomplish the balancing of the load amongst the four base stations 20, 30, 40 and 50, the base stations had to recognize the imbalance in their consumed resource blocks as shown in FIG. 1 and then determine how many resource blocks to offload and the associated UEs to handover in order to efficiently and more uniformly balance the load. As will be understood by those skilled in the art, beginning with the system 10 as illustrated in FIG. 1 , there are a variety of results that could balance the system 10 in FIG. 2 with specific UEs having been handed over to specific base stations. As such, it should be clear that FIG. 2 represents one example result of balancing the load in the illustrated system 10.

[0027] FIG. 3 is a block diagram illustrating an example base station 20 in a mobile communication system according to an embodiment of the present invention. In the illustrated embodiment, the base station 20 comprises a load balancing module 100, a load analyzer module 110, a load reporter module 120, a handover module 130 and a communication module 140. The base station 20 also has a data storage area 22. The modules 100, 110, 120, 130 and 140 may be implemented in hardware or software or some combination of the two.

[0028] The load balancing module 100 is configured to manage the load balancing process and communicates with the other modules to do so. The load balancing module is configured to monitor its own load as well as the load of neighboring base stations for which it has valid load information.

[0029] The load analyzer module 110 is configured to analyze the load of base station 20 and neighboring base stations and compare the load of base station 20 with neighboring base stations and compare the relative loads of neighboring base stations to determine if the present load of base station 20 and its neighboring base stations is unbalanced. The load analyzer module 110 may analyze loads against predetermine thresholds that may be established, for example, by the operator of the mobile communication system. The load analyzer module 110 may also analyze loads against a calculated value such as an average or a peak or a trough.

[0030] The load reporter module 120 is configured to compile information related to the load of base station 20 and provide such load reports to the balancing module 100 upon request. The load reporter module 120 is also configured to parse through load reports from neighboring base stations and provide load related information to the balancing module 100 or the load analyzer module 110.

[0031] The handover module 130 is configured to initiate a handover process to transfer UEs from base station 20 to a neighboring base station. The handover module 130 is also configured to respond to handover processes initiated by neighboring base stations to transfer UEs from neighboring base stations to base station 20. [0032] The communication module 140 is configured to manage wired or wireless communications for base station 20. For example, the communication module 140 manages wireless communications with UEs and also manages wireless or wired communication between base station 20 and neighboring base stations.

[0033] FIG. 4 is a flow diagram illustrating an example process for balancing resource blocks according to an embodiment of the present invention. The illustrated process may be carried out by two or more base stations in a mobile communication system such as previously described with respect to FIGS 1-3. Initially, in step 200 a first base station receives periodic load reports from its neighboring base stations. A load report includes certain information about the amount of resources (such as the number of resource blocks) that the base station producing the report is currently handling. The base station analyzes the load reports in step 210 to determine if there is an imbalance in load between the first base station and a neighboring base station. If the difference between the load of the first base station and the load of a neighboring base station does not exceed a predetermine threshold value, as determined in step 220, then the process loops back and the base station continues to receive and analyze load reports from its neighboring base stations.

[0034] However, if step 220 determines that there is an imbalance in load between the first base station and the second base station that does exceed the predetermine threshold value, then the first base station sends its own load report to the second base station. The second base station is the base station that provided the load report that was analyzed by the first base station to identify an imbalance in load between the first and second base stations. It should be noted that the imbalance may be that the first base station has too high of a load or that the first base station has too low of a load relative to the second base station.

[0035] The load report sent by the first base station in response to detecting an imbalance in load between the first and second base stations advantageously includes the first base station's current load and may include information related to its load condition, the neighbor load supply. The neighbor load supply is the MaxSink parameter or the MinSource parameter depending on the nature of the imbalance in loads. The MaxSink value is the maximum number of resource blocks (units of load) that the first base station will accept from the second base station and is sent when the first base station's load is lower than the second base station's load. The value of this parameter could be determined by the first base station by considering the load conditions of one or more neighbors of the first base station. The MinSource value is the minimum number of resource blocks that the first base station needs to offload to the second base station and is sent when the first base station's load is higher than the second base station's load. The value of this parameter could also be determined by the first base station by considering the load conditions of one or more neighbors of the first base station.

[0036] In response to sending its load report with the neighbor load supply information, in step 240, the first base station receives a responsive load report from the second base station. The responsive load report from the second base station includes its current load and may also include neighbor load supply information for the second base station, consisting of either the MaxSink parameter or the MinSource parameter. This parameter's value could be determined by the second base station by considering the load conditions of the first base station and the other neighbors of the second base station. Upon receiving the responsive load report, the first base station analyzes the load report and may send another load report to the second base station with updated neighbor load supply information. In step 250 the first and second base stations perform handovers to either (1) transfer UEs and their respective resource blocks from the first base station to the second base station when the first base station's load was too high; or (2) transfer UEs and their respective resource blocks from the second base station to the first base station when the first base station's load was too low. As will be understood by those skilled in the art, the initiating base station in a handover is referred to as the source and the other base station in the handover is referred to as the target. In case (1) above, the first base station is the handover source and the second base station is the handover target and vice versa for case (2) above.

[0037] In one example embodiment, the imbalance in load is that the first base station has a higher present load than the second base station. Accordingly, the handover process transfers load from the first base station to the second base station. In an alternative embodiment, the imbalance in load is that the first base station has a lower present load than the second base station such that the handover process transfers load from the second base station to the first base station.

[0038] FIG. 5 is a flow diagram illustrating an example process for balancing resource blocks according to an embodiment of the present invention where periodic load reports are not sent between base stations. The illustrated process may be carried out by two or more base stations in a mobile communication system such as previously described with respect to FIGS 1-3. Initially, in step 300, a first base station obtains load balancing threshold values which it uses to compare its load with its neighbor loads. The thresholds may be configured by a network operator, such as through a terminal port or through an operations and maintenance system. The thresholds may be obtained from another base station or other network node. The thresholds may represent the maximum load difference allowed between two base stations expressed as an absolute difference value or as a percentage difference. A first base station may receive absolute high and low load values from a second base station, where the second base station sets the high load threshold to be its current load plus the maximum allowed load difference and sets the low load threshold to be its current load minus the maximum allowed load difference. For example this method could be used when the first base station has not obtained the load difference thresholds. [0039] Next, in step 310, the first base station determines that its present load has crossed a load difference threshold value. This means that the load of the first base station is too far out of balance with a second base station. This determination can be made by the first base station by analyzing its own load and comparing that load to a predetermined threshold. In one embodiment, the first base station obtains load balance difference thresholds and when it receives a load report from the second base station, it compares it with its current load and if the difference is greater than the allowed threshold, a load imbalance event is determined. In another embodiment, the first base station receives absolute high and low threshold load values from a second base station. When the first base station's load becomes higher than the high threshold or lower than the low threshold a load imbalance event is determined.

[0040] Next, in step 320, the first base station sends its load report with its current load and neighbor load supply information (MinSource or MaxSink) to the second base station to notify the second base station of a potential load imbalance event. The second base station compares its current load with the first base station's load received in the load report in order to test the load imbalance event. The second base station sends a responsive load report to the first base station with its current load and includes neighbor load supply information. The first base station receives the responsive load report in step 330 and analyzes the responsive load report from the second base station to confirm the load imbalance event, as shown in step 340. If the load imbalance event is not confirmed in step 340, the first base station loops back to step 310 (not shown) and continues to compare its load with the load of the second base station using the new load information contained in the load report from the second base station.

[0041] Next, in step 350, the first base station performs handovers to transfer UEs and their respective resource blocks either from or to the second base station to balance the load in the mobile communication system. As will be understood by those skilled in the art, although the present description is focused on the interface between two neighbor base stations, the methods of the invention may be applied on an ongoing basis between a first base station and multiple neighbors with applicable coordination.

[0042] FIG. 6 is a block diagram illustrating an example pair of base stations 405 and 410 balancing resource blocks in a mobile communications system 500 according to an embodiment of the present invention. In the illustrated embodiment, the base station 405 initially sends a resource status request 420 to base station 410 in order to request periodic load reports. In response, base station 410 sends a resource status response 430 to the base station 405. Next, the base station 410 sends periodic resource status updates 440, 442, 444, 446, 448 and 450 containing load reports according to the specifications in the resource status request message from base station 405 and base station 405 compares its current load with the load of base station 410 received in the resource status updates.

[0043] In alternative embodiments, the reporting period may vary in time. For example, in one embodiment, the period may adjust based on the changing load of base station 410 such that if its load remains relatively constant (e.g., within a certain range) then no resource status updates are sent. In this fashion, signaling between base stations can be reduced even further.

[0044] When base station 405 receives resource status update 450, it detects event 470, which corresponds to a load imbalance larger than the threshold value. As a result of detecting event 470, base station 405 sends resource status update 480 to base station 410. The resource status update 480 advantageously includes the current load and neighbor load supply information (MinSource or MaxSink) for base station 405. In response, base station 410 sends resource status update 490 to base station 405. The resource status update 490 advantageously includes the current load and neighbor load supply information (MinSource or MaxSink) for base station 410. Base station 405 and base station 410 subsequently proceed to perform handovers 495 to balance the load in the mobile communication system 500.

[0045] It should be noted that the event detected by base station 405 could be related to the base station 410 having a load that is too high or too low with respect to the load of base station 405. Alternatively, the event may be related to the base station 410 having a load that is too high or too low with respect to a predetermined threshold that may be, for example, established by an operator of the mobile communication system. Alternatively, the event may be related to the base station 410 having a load that is too high or too low with respect to a percentage of one or more predetermined values such as a high and low value or an average value.

[0046] FIG. 7 is a block diagram illustrating an example pair of base stations 406 and 411 balancing resource blocks in a mobile communications system 400 according to an embodiment of the present invention. In the illustrated embodiment, the base station 406 obtains load balance difference thresholds 355. The load balance difference thresholds 355 may be obtained via network operator configuration, obtained from another base station, obtained from another network node, or obtained from any other source of load balance difference thresholds. The base station 406 also obtains an initial load report from base station 411. The initial load report is provided in the resource status update 365. Base station 406 initially detects a potential event 360. Base station 406 may detect the potential event 360 by determining that its current load has exceeded a predetermined threshold relative to base station 411.

[0047] Upon detection of the potential event 360, base station 406 sends a resource status update 370 to base station 411. The resource status update 370 advantageously includes the current load and neighbor load supply information (MinSource or MaxSink) for base station 406. Using the resource status update 370 from base station 406, base station 411 is able to confirm that the potential event 360 is an actual event by comparing its current load with the load of base station 406 received in the resource status update. In response, base station 411 sends resource status update 380 to base station 406. The resource status update 380 advantageously includes the current load and neighbor load supply information (MinSource or axSink) for base station 411. Using the resource status update 380 from base station 411 , base station 406 is able to determine that the potential event 360 is an actual confirmed event 390. Upon confirmation, base station 406 and base station 411 proceed to perform handovers 395 to balance the load in the mobile communication system 400. In one embodiment, base station 41 sends resource status update 380 regardless of whether event 360 is confirmed or not confirmed in order to provide updated load information to base station 406.

[0048] It should be noted that the event detected by base station 406 could be related to the base station 411 having a load that is too high or too low with respect to the load of base station 406. Alternatively, the event may be related to the base station 411 having a load that is too high or too low with respect to a predetermined threshold that may be, for example, established by an operator of the mobile communication system. Alternatively, the event may be related to the base station 411 having a load that is too high or too low with respect to a percentage of one or more predetermined values such as a high and low value or an average value.

[0049] FIG. 8 is a block diagram illustrating an example computer system 550 that may be used in connection with various embodiments described herein. For example, referring to FIG. 1 , the computer system 550 may be used as or in conjunction with a base station 20 or a UE 60. However, other computer systems and/or architectures may also be used, as will be clear to those skilled in the art.

[0050] The computer system 550 preferably includes one or more processors, such as processor 560. Additional processors may be provided, such as an auxiliary processor to manage input/output, an auxiliary processor to perform floating point mathematical operations, a special-purpose microprocessor having an architecture suitable for fast execution of signal processing algorithms (e.g., digital signal processor), a slave processor subordinate to the main processing system (e.g., back-end processor), an additional microprocessor or controller for dual or multiple processor systems, or a coprocessor. Such auxiliary processors may be discrete processors or may be integrated with the processor 560.

[0051] The processor 560 is preferably connected to a communication bus 555. The communication bus 555 may include a data channel for facilitating information transfer between storage and other peripheral components of the computer system 550. The communication bus 555 further may provide a set of signals used for communication with the processor 560, including a data bus, address bus, and control bus (not shown). The communication bus 555 may comprise any standard or non-standard bus architecture such as, for example, bus architectures compliant with industry standard architecture ("ISA"), extended industry standard architecture ("EISA"), Micro Channel Architecture ("MCA"), peripheral component interconnect ("PCI") local bus, or standards promulgated by the Institute of Electrical and Electronics Engineers ("IEEE") including IEEE 488 general-purpose interface bus ("GPIB"), IEEE 696/S-100, and the like.

[0052] Computer system 550 preferably includes a main memory 565 and may also include a secondary memory 570. The main memory 565 provides storage of instructions and data for programs executing on the processor 560. The main memory 565 is typically semiconductor-based memory such as dynamic random access memory ("DRAM") and/or static random access memory ("SRAM"). Other semiconductor-based memory types include, for example, synchronous dynamic random access memory ("SDRAM"), Rambus dynamic random access memory ("RDRAM"), ferroelectric random access memory ("FRAM"), and the like, including read only memory ("ROM").

[0053] The secondary memory 570 may optionally include a internal memory 575 and/or a removable medium 580, for example a floppy disk drive, a magnetic tape drive, a compact disc ("CD") drive, a digital versatile disc ("DVD") drive, etc. The removable medium 580 is read from and/or written to in a well-known manner. Removable storage medium 580 may be, for example, a floppy disk, magnetic tape, CD, DVD, SD card, etc.

[0054] The removable storage medium 580 is a non-transitory computer readable medium having stored thereon computer executable code (i.e., software) and/or data. The computer software or data stored on the removable storage medium 580 is read into the computer system 550 for execution by the processor 560.

[0055] In alternative embodiments, secondary memory 570 may include other similar means for allowing computer programs or other data or instructions to be loaded into the computer system 550. Such means may include, for example, an extemal storage medium 595 and an interface 570. Examples of external storage medium 595 may include an extemal hard disk drive or an external optical drive, or and extemal magneto-optical drive.

[0056] Other examples of secondary memory 570 may include semiconductor- based memory such as programmable read-only memory ("PROM"), erasable programmable read-only memory ("EPROM"), electrically erasable read-only memory ("EEPROM"), or flash memory (block oriented memory similar to EEPROM). Also included are any other removable storage media 580 and communication interface 590, which allow software and data to be transferred from an extemal medium 595 to the computer system 550.

[0057] Computer system 550 may also include a communication interface 590. The communication interface 590 allows software and data to be transferred between computer system 550 and external devices (e.g. printers), networks, or information sources. For example, computer software or executable code may be transferred to computer system 550 from a network server via communication interface 590. Examples of communication interface 590 include a modem, a network interface card ("NIC"), a wireless data card, a communications port, a PCMCIA slot and card, an infrared interface, and an IEEE 1394 fire-wire, just to name a few.

[0058] Communication interface 590 preferably implements industry promulgated protocol standards, such as Ethernet IEEE 802 standards, Fiber Channel, digital subscriber line ("DSL"), asynchronous digital subscriber line ("ADSL"), frame relay, asynchronous transfer mode ("ATM"), integrated digital services network ("ISDN"), personal communications services ("PCS"), transmission control protocol/Internet protocol ("TCP/IP"), serial line Internet protocol/point to point protocol ("SLIP/PPP"), and so on, but may also implement customized or non-standard interface protocols as well.

[0059] Software and data transferred via communication interface 590 are generally in the form of electrical communication signals 605. These signals 605 are preferably provided to communication interface 590 via a communication channel 600. In one embodiment, the communication channel 600 may be a wired or wireless network, or any variety of other communication link. Communication channel 600 carries signals 605 and can be implemented using a variety of wired or wireless communication means including wire or cable, fiber optics, conventional phone line, cellular phone link, wireless data communication link, radio frequency ("RF") link, or infrared link, just to name a few.

[0060] Computer executable code (i.e., computer programs or software) is stored in the main memory 565 and/or the secondary memory 570. Computer programs can also be received via communication interface 590 and stored in the main memory 565 and/or the secondary memory 570. Such computer programs, when executed, enable the computer system 550 to perform the various functions of the present invention as previously described.

[0061] In this description, the term "computer readable medium" is used to refer to any non-transitory computer readable storage media used to provide computer executable code (e.g., software and computer programs) to the computer system 550. Examples of these media include main memory 565, secondary memory 570 (including internal memory 575, removable medium 580, and external storage medium 595), and any peripheral device communicatively coupled with communication interface 590 (including a network information server or other network device). These non-transitory computer readable mediums are means for providing executable code, programming instructions, and software to the computer system 550.

[0062] In an embodiment that is implemented using software, the software may be stored on a computer readable medium and loaded into computer system 550 by way of removable medium 580, interface 570, or communication interface 590. In such an embodiment, the software is loaded into the computer system 550 in the form of electrical communication signals 605. The software, when executed by the processor 560, preferably causes the processor 560 to perform the inventive features and functions previously described herein.

[0063] The system 550 also includes optional wireless communication components that facilitate wireless communication over a voice and over a data network. The wireless communication components comprise an antenna system 620, a radio system 615 and a baseband system 610. In the communication device 550, radio frequency ("RF") signals are transmitted and received over the air by the antenna system 620 under the management of the radio system 6 5.

[0064] In one embodiment, the antenna system 620 may comprise one or more antennae and one or more multiplexors (not shown) that perform a switching function to provide the antenna system 620 with transmit and receive signal paths. In the receive path, received RF signals can be coupled from a multiplexor to a low noise amplifier (not shown) that amplifies the received RF signal and sends the amplified signal to the radio system 615.

[0065] In alternative embodiments, the radio system 615 may comprise one or more radios that are configured to communication over various frequencies. In one embodiment, the radio system 615 may combine a demodulator (not shown) and modulator (not shown) in one integrated circuit ("IC"). The demodulator and modulator can also be separate components. In the incoming path, the demodulator strips away the RF carrier signal leaving a baseband receive audio signal, which is sent from the radio system 615 to the baseband system 610.

[0066] If the received signal contains audio information, then baseband system 610 decodes the signal and converts it to an analog signal. Then the signal is amplified and sent to a speaker. The baseband system 610 also receives analog audio signals from a microphone. These analog audio signals are converted to digital signals and encoded by the baseband system 610. The baseband system 620 also codes the digital signals for transmission and generates a baseband transmit audio signal that is routed to the modulator portion of the radio system 615. The modulator mixes the baseband transmit audio signal with an RF carrier signal generating an RF transmit signal that is routed to the antenna system and may pass through a power amplifier (not shown). The power amplifier amplifies the RF transmit signal and routes it to the antenna system 620 where the signal is switched to the antenna port for transmission.

[0067] The baseband system 610 is also communicatively coupled with the processor 560. The central processing unit 560 has access to data storage areas 565 and 570. The central processing unit 560 is preferably configured to execute instructions (i.e., computer programs or software) that can be stored in the memory 565 or the secondary memory 570. Computer programs can also be received from the baseband processor 610 and stored in the data storage area 565 or in secondary memory, or executed upon receipt. Such computer programs, when executed, enable the communication device 550 to perform the various functions of the present invention as previously described. For example, data storage areas 565 may include various software modules (not shown) that perform the various functions of the present invention as previously described. [0068] Various embodiments may also be implemented primarily in hardware using, for example, components such as application specific integrated circuits ("ASICs"), or field programmable gate arrays ("FPGAs"). Implementation of a hardware state machine capable of performing the functions described herein will also be apparent to those skilled in the relevant art. Various embodiments may also be implemented using a combination of both hardware and software.

[0069] Furthermore, those of skill in the art will appreciate that the various illustrative logical blocks, modules, circuits, and method steps described in connection with the above described figures and the embodiments disclosed herein can often be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled persons can implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the invention. In addition, the grouping of functions within a module, block, circuit or step is for ease of description. Specific functions or steps can be moved from one module, block or circuit to another without departing from the invention.

[0070] Moreover, the various illustrative logical blocks, modules, and methods described in connection with the embodiments disclosed herein can be implemented or performed with a general purpose processor, a digital signal processor ("DSP"), an ASIC, FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor can be a microprocessor, but in the alternative, the processor can be any processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0071] Additionally, the steps of a method or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium including a network storage medium. An exemplary storage medium can be coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The processor and the storage medium can also reside in an ASIC.

[0072] The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, it is to be understood that the description and drawings presented herein represent a presently preferred embodiment of the invention and are therefore representative of the subject matter which is broadly contemplated by the present invention. It is further understood that the scope of the present invention fully encompasses other embodiments that may become obvious to those skilled in the art and that the scope of the present invention is accordingly not limited.

Claims

1. A computer implemented method for balancing load in a mobile communication system, where one or more processors are programmed to perform steps comprising:

receiving at a first base station periodic load reports from a plurality of neighboring base stations;

analyzing the periodic load reports from the neighboring base stations;

determining that the load of a second neighboring base station exceeds a predetermined difference threshold value relative to the current load of the first base station;

sending a load report from the first base station to the second base station; receiving at the first base station a load report from the second base station; and

performing handovers between the first base station and the second base station to balance load in the mobile communication system.

2. The method of claim 1 , wherein the load report from the first base station and the load report from the second base station each include neighbor load supply information.

3. The method of claim 2, wherein the neighbor load supply information in the load report from the second base station includes information about the relative load between the second base station and at least one neighbor of the second base station, wherein the at least one neighbor of the second base station is not the first base station.

4. The method of claim 3, wherein the performing handovers step is based at least in part on a load imbalance between the second base station and the at least one neighbor of the second base station.

5. The method of claim 2, wherein the neighbor load supply information from the first base station includes a maximum resource sink value.

6. The method of claim 2, wherein the neighbor load supply information from the first base station includes a minimum resource source value.

7. The method of claim 2, wherein the neighbor load supply information from the second base station includes a maximum resource sink value.

8. The method of claim 2, wherein the neighbor load supply information from the second base station includes a minimum resource source value.

9. A computer implemented method for balancing load in a mobile communication system, where one or more processors are programmed to perform steps comprising:

monitoring at a first base station the load of the first base station;

determining at the first base station that the load of the first base station exceeds a predetermined value based on the difference between the current load of the first base station and a stored value of the load of one or more neighbor base stations;

sending a request for a load report from the first base station to one or more neighbor base stations;

receiving at the first base station a load report from at least one of the one or more neighbor base stations;

analyzing the received load reports;

determining that the current load of a second base station exceeds a predetermined difference threshold value relative to the current load of the first base station; and performing handovers with at least one of the one or more neighbor base stations to balance load in the mobile communication system.

10. The method of claim 9, wherein the load report from the second base station includes neighbor load supply information.

11. The method of claim 10, wherein the neighbor load supply information in the load report from the second base station includes information about the relative load between the second base station and at least one neighbor of the second base station, wherein the at least one neighbor of the second base station is not the first base station.

12. The method of claim 9, wherein the load report from at least one of the one or more neighbor base stations includes a maximum resource sink value.

13. The method of claim 9, wherein the load report from at least one of the one or more neighbor base stations includes a minimum resource source value.

14. A plurality of executable instructions stored in one or more non-transitory computer readable mediums, the instructions for causing one or more processors to perform the steps for balancing load in a mobile communication system, the steps comprising:

analyzing the periodic load reports from the neighboring base stations;

15. The method of claim 14, wherein the periodic load reports include neighbor load supply information.

16. The method of claim 15, wherein the determining step further comprises using the neighbor load supply information to calculate a difference between relative loads.

17. The method of claim 14, wherein the load report from the first base station includes a maximum resource sink value.

18. The method of claim 14, wherein the load report from the first base station includes a minimum resource source value.

19. The method of claim 14, wherein the load report from the second base station includes a maximum resource sink value.

20. The method of claim 14, wherein the load report from the second base station includes a minimum resource source value.

21. A plurality of executable instructions stored in one or more non-transitory computer readable mediums, the instructions for causing one or more processors to perform the steps for balancing load in a mobile communication system, the steps comprising:

monitoring at a first base station the load of the first base station; redetermining at the first base station that the load of the first base station exceeds a predetermined value based on the difference between the current load of the first base station and a stored value of the load of one or more neighbor base stations;

analyzing the received load reports;

determining that the current load of a second neighboring base station exceeds a predetermined difference threshold value relative to the current load of the first base station; and

performing handovers with one or more of the neighbor base stations to balance the load in the mobile communication system.

22. The medium of claim 21 , wherein the load report from the second base station includes neighbor load supply information.

23. The medium of claim 22, wherein the neighbor load supply information in the load report from the second base station includes information about the relative load between the second base station and at least one neighbor of the second base station, wherein the at least one neighbor of the second base station is not the first base station.

24. The medium of claim 21 , wherein the load report from at least one of the one or more neighbor base stations includes a maximum resource sink value.

25. The medium of claim 21 , wherein the load report from at least one of the one or more neighbor base stations includes a minimum resource source value.

26. A wireless communication base station system comprising:

a non-transitory computer readable medium configured to store executable programmed modules;

a processor communicatively coupled with the non-transitory computer readable medium configured to execute programmed modules stored therein;

a load balancing module stored in the non-transitory computer readable medium and configured to be executed by the processor, the load balancing module configured to monitor the current load of the wireless communication base station system, monitor the current load of one or more neighbor base station systems and determine when to transfer user equipment between base station systems;

a load analyzer module stored in the non-transitory computer readable medium and configured to be executed by the processor, the load analyzer module configured to analyze the current load of the wireless communication base station system and the current load of the one or more neighbor base station systems;

a load reporter module stored in the non-transitory computer readable medium and configured to be executed by the processor, the load reporter module configured to parse load reports received from the one or more neighbor base station systems and provide load related information to the load analyzer module and the load balancing module; and

a handover module stored in the non-transitory computer readable medium and configured to be executed by the processor, the handover module configured to transfer user equipment from the wireless communication base station system to the one or more neighbor base station systems and transfer user equipment to the wireless communication base station system from the one or more neighbor base station systems in response to an instruction from the load balancing module.

27. The system of claim 26, wherein the load balancing module is further configured to instruct the handover module to perform handovers with one or more neighbor base stations based at least in part on the current load of at least one neighbor base station.

28. The system of claim 26, wherein the load balancing module is further configured to monitor the current load of one or more neighbor base station systems by receiving neighbor load supply information from said one or more neighbor base station systems.

29. The system of claim 28, wherein the neighbor load supply information from a first neighbor includes information about the load of the first neighbor's neighbors.

30. The system of claim 29, wherein the load balancing module is further configured to instruct the handover module to perform handovers with one or more neighbor base stations based at least in part on a load imbalance between first neighbor and the first neighbor's neighbors.