Patent Publication Number: US-9428076-B2

Title: Method and system for more efficient operation of plug-in electric vehicles

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 12/699,790, entitled “Method and System for More Efficient Operation of Plug-In Electric Vehicles,” filed on Feb. 3, 2010, now U.S. Pat. No. 8,855,840, the entire disclosure of which is hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Field 
     The present invention relates to a more efficient operation of plug-in electric vehicles. 
     2. Description of the Related Art 
     Conventional plug-in electric vehicles operate in a charge depletion mode until a minimum charge value has been reached and thereafter switches to a charge sustaining mode. However, such operations can be inefficient if the vehicle will travel a significant distance in charge sustaining mode. During such a trip, the state of charge (“SOC”) of an energy storage unit will be depleted during situations where it would be more efficient to use the energy conversion unit utilizing stored fuel to propel the vehicle and/or increase the SOC; or during the charge sustaining mode where the SOC is being maintained at some minimal level even when it is more efficient to increase or decrease the SOC via the energy conversion unit utilizing stored fuel. 
     Furthermore, conventional plug-in electric vehicles which have been operating for some time will inevitably operate in the charge sustaining mode maintaining a minimal SOC in the energy storage unit. However, the conventional plug-in electric vehicle may desire to enter a city, which is concerned about emissions. The city may prohibit the plug-in electric vehicle from utilizing its engine to provide direct motive power, generating electrical power to operate the motor, and/or charging the energy storage unit at all. Thus, the plug-in electric vehicle must operate in the charge depletion mode. Since conventional plug-in electrical vehicles only maintain a minimal SOC in the energy storage unit while in the charge sustaining mode, the plug-in electric vehicles will not be able to travel very far before they needs to be plugged in to be charged. Alternatively, conventional plug-in electric vehicles must avoid the city altogether. Neither outcomes are particularly desirable for a user who drives a plug-in electric vehicle and wants to travel through the city. 
     Thus, there is a need for a more efficient operation of automobiles, such as plug-in electric vehicles. 
     SUMMARY 
     The present invention relates to a more efficient operation of automobiles, such as plug-in electric vehicles. In one embodiment, the present invention is an automobile, such as a plug-in electric vehicle, which includes an energy conversion unit, an energy storage unit, a user selection unit, a global positioning system, and a control unit. The automobile can operate in a default mode, which is either the charge depletion mode or the charge sustaining mode. However, upon a user input, the automobile such as the energy conversation unit and/or the energy storage unit can operate in an extended charging mode or a forced charging mode. In the extended charging mode, the SOC is increased or decreased over a predetermined charging range allowing for the SOC to be increased when it is efficient to do so and for the SOC to be decreased when it is efficient to do so. In the forced charging mode, the SOC is increased until a predetermined charge limit is reached. This allows the energy storage unit to have a large SOC which can be depleted if necessary to move the automobile. 
     Furthermore, the present invention can also use a global positioning system signal to operate in the charge depletion mode, the charge sustaining mode, the extended charging mode, and/or the forced charging mode. The global positioning system signal can allow the control unit to determine a distance from the automobile to a target location, driver behavior, traffic conditions, and/or road conditions, and depending on the location of the automobile and/or the distance to the target location, to operate the automobile in the charge depletion mode, the charge sustaining mode, the extended charging mode, and/or the forced charging mode. This allows the automobile to operate in the most desirable mode based on distance to the target location. 
     In one embodiment, the present invention is a method for operating an automobile including operating the automobile in a default charging mode, and operating the automobile in an extended charging mode. 
     In another embodiment, the present invention is a method for operating an automobile including operating the automobile in a charge depletion mode, the charge depletion mode substantially depleting an energy storage unit of the automobile, operating the automobile in a charge sustaining mode, the charge sustaining mode charging the energy storage unit in the automobile in a first predetermined charging range, and operating the automobile in a forced charging mode, the forced charging mode charging the energy storage unit of the automobile until the energy storage unit of the automobile has a substantially full charge, and thereafter maintaining the energy storage unit of the automobile at the substantially full charge. 
     In yet another embodiment, an automobile including an energy conversion unit, an energy storage unit connected to the energy conversion unit, the energy storage unit having a charge level, and supplying power to the energy conversion unit, or receiving power from the energy conversion unit, and a control unit electrically connected to the energy storage unit of the energy conversion unit, the control unit selecting the energy storage unit or the energy conversion unit to operate in a default charging mode, or an extended charging mode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features, obstacles, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, wherein: 
         FIG. 1  is a block diagram of an automobile according to an embodiment of the present invention; 
         FIG. 2  is a block diagram of a fuel conversion system according to an embodiment of the present invention; 
         FIG. 3  is a block diagram of a fuel conversion system according to another embodiment of the present invention; 
         FIG. 4  is an operation graph of an engine and/or a generator according to an embodiment of the present invention; 
         FIG. 5  is a graph of strength of charge over distance for various modes of operation for an automobile according to an embodiment of the present invention; and 
         FIG. 6  is a process according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Apparatus, systems and methods that implement the embodiments of the various features of the present invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate some embodiments of the present invention and not to limit the scope of the present invention. Throughout the drawings, reference numbers are re-used to indicate correspondence between referenced elements. 
     In one embodiment, the present invention includes an automobile  100  as shown in  FIG. 1 . The automobile  100  includes an energy conversion unit  102  (e.g., a first or main energy conversion unit), an energy conversion unit  132  (e.g., a second or auxiliary energy conversion unit), an energy storage unit  104 , a control unit  106 , a user selection unit  108 , a global positioning system  110 , and/or electronic devices  122 . The automobile  100  can be, for example, a plug-in electric vehicle, a hybrid vehicle, a vehicle with a combustion engine, a hydrogen vehicle, a natural gas vehicle, and/or any other types of vehicles. The electronic devices  122  can be, for example, a radio, an air conditioning unit, headlights, lamps, sensors, power windows, or any other devices in the automobile  100  which requires or utilizes energy. 
     The energy conversion unit  102  can be connected to the control unit  106  and/or the energy storage unit  104 . The energy conversion unit  102  can also be optionally connected to the energy conversion unit  132 . The energy conversion unit  102  can include a fuel conversion system  124  allowing the energy conversion unit  102  to convert fuel to electrical energy. In one embodiment, as seen in  FIG. 2 , the fuel conversion system  124  can include an engine  128  connected to a generator  126 . The operation of the engine  128  can generate motive force to move the automobile  100 . However, the generator  126  can also generate energy from the operation of the engine  128 , which can be transferred to the energy storage unit  104  and/or the energy conversion unit  132 . 
     In another embodiment, as shown in  FIG. 3 , the fuel conversion system  124  includes a hydrogen conversion system  130 . The hydrogen conversion system  130  can include, for example, hydrogen fuel cells which store and/or convert hydrogen fuel into energy. The energy can then be transferred to the energy storage unit  104 . The hydrogen conversion system  130  may not provide motive force to move the automobile  100 ; however, the hydrogen conversion system  130  can provide energy which can be used by the energy conversion unit  132  to provide motive force to move the automobile  100 . Furthermore, although examples of the fuel conversion system  124  are disclosed in  FIG. 2  and  FIG. 3 , any other type of fuel conversion system may be used such that fuel may be converted into energy. In addition, although examples refer to the fuel conversion system  124  as disclosed in  FIG. 2 , any such examples may be applicable to the fuel conversion system  124  as disclosed in  FIG. 3  or other types of fuel conversion systems, too. 
     The energy conversion unit  132  is connected to the energy storage unit  104  and/or the control unit  106 . The energy conversion unit  132  is also optionally connected to the energy conversion unit  102 . The energy conversion unit  132  can be, for example, a motor. The energy conversion unit  132  can use energy from the energy storage unit  104  and/or the energy conversion unit  102  to provide motive force to move the automobile  100 . However, the energy conversion unit  132  can also capture energy from regenerative processes such as braking. Thus, the energy conversion unit  132  can transfer the captured energy to the energy storage unit  104  or use the captured energy stored in the energy storage unit  104  to move the automobile  100 . The energy conversion unit  132  can also use energy from the energy conversion unit  102  to move the automobile  100 . 
     The energy storage unit  104  is connected to the energy conversion unit  102 , the energy conversion unit  132 , the control unit  106 , and/or the electronic devices  122 . The energy storage unit  104  receives energy from the energy conversion unit  102  and/or the energy conversion unit  132  and stores the energy. The energy storage unit  104  can have, for example, a charge level, or state of charge (“SOC”) corresponding to an amount of energy stored in the energy storage unit  104 . The stored energy in the energy storage unit  104  can be used to power any electronic devices  122  within the automobile  100  and/or move the automobile  100 . The energy storage unit  104  can be, for example, a battery, a mechanical energy storage device, and/or any other type of device which can store energy. 
     The energy conversion unit  102  and/or the energy storage unit  104  can operate in various modes such as a default mode, an extended charging mode, and/or a forced charging mode. The default mode can include, for example, a charge depletion mode and/or a charge sustaining mode. In the charge depletion mode, the energy conversion unit  102  does not provide energy to the energy storage unit  104  and the energy storage unit  104  is depleted. The energy storage unit  104  can be depleted, for example, by providing energy to the energy conversion unit  132 , such as to move the automobile  100 , and/or providing energy to the electronic devices  122  within the automobile  100 . In one embodiment, the energy conversion unit  102  can be inoperative and the energy conversion unit  132  supplies the only motive force to move the automobile  100 . 
     For example, regardless of whether it is more efficient or inefficient to do so, the energy storage unit  104  is depleted and the SOC is decreased. For example, the SOC of the energy unit  104  can be depleted, even when it may be more efficient to be operating the engine  128  and/or the generator  126  ( FIG. 2 ) to move the automobile  100  and/or to generate energy which can be stored in the energy storage unit  104  for later use. 
     For example, it may take only 15 kW to move the automobile  100 . In the charge depletion mode, the 15 kW is drawn from the energy storage unit  104  by the energy conversion unit  132  and used by the energy conversion unit  132  to move the automobile  100 . The energy conversion unit  102  can be inoperative and therefore, the engine  128  and the generator  126  can be inoperative, too. Thus, no energy is generated by the operation of the engine  128  and the generator  126 . However, in certain situations, instead of using the energy conversion unit  132 , it may be more efficient to have the engine  128  and the generator  126  generate 21 kW, use 15 kW to move the automobiles  100 , and store the remaining 6 kW in the energy storage unit  104 . 
     This can be illustrated, for example, in  FIG. 4 . In  FIG. 4 , lines  134   a ,  134   b , and  134   c  represent the lines of constant power for the engine  128  and the generator  126 . The line  134   a  indicates the engine  128  operation which generates 15 kW of power, while the line  134   b  indicates the engine  128  operation which generates 18 kW of power, and the line  134   c  indicates the engine  128  operation which generates 21 kW of power. The lines  136  indicate a fuel efficiency of the engine  128  and/or the generator  126  on a per g/(kW-hr) basis. The area  138  indicates the actual operation of the engine  128  and the generator  126  in the automobile  100 . As can be seen at the point  140 , the engine  128  generates approximately 15 kW of power, while at the point  142 , the engine  128  generates approximately 21 kW of power. However, on a per g/(kW-hr) basis, it is more efficient to generate 21 kW of power than it is to generate 15 kW of power. 
     During the charge sustaining mode, the energy conversion unit  102  and/or the energy storage unit  104  maintains the SOC at a relatively constant energy level with deviations to the constant energy level minimized, or with a minimal charging range. For example, regardless of whether the automobile  100  it is more efficient or inefficient to do so, the SOC of the energy storage unit  104  can vary in a first predetermined charging range. Thus, referring to  FIG. 4 , the engine  128  and the generator  126  may only operate at the point  140  to generate the 15 kW necessary to move the automobile  100  instead of at the point  142  to generate an additional 6 kW in addition to the 15 kW necessary to move the automobile  100 . As can be seen, this can lead to a more inefficient operation of the automobile  100  since it may be more efficient to operate the automobile  100  at the point  142  instead of the point  140 . 
     The first predetermined charging range can be, for example, a charging range of 10% SOC to 15% SOC. In one embodiment, the SOC can vary from a SOC level of 10% SOC to 20% SOC or a SOC level of 10% SOC to 25% SOC, which is a first predetermined charging range of 10% SOC (20% SOC−10% SOC) to 15% SOC (25% SOC−10% SOC). Thus, the energy conversion unit  102  can supply power to the energy storage unit  104  to maintain the SOC within the first predetermined charging range. 
     In the extended charging mode, the conversion unit  102  and/or the energy storage unit  104 , opportunistically charges the energy storage unit  104  within a second predetermined charging range, which is an extended charging range. The conversion unit  132  can opportunistically charge and/or deplete the energy storage unit  104  within the second predetermined charging range. In one embodiment, the second predetermined charging range can be, for example, 60% SOC to 80% SOC. The second predetermined charging range can be any charging range greater than the first predetermined charging range. 
     For example, the SOC of the energy storage unit can have a varying SOC level of 20% SOC to 80% SOC, and/or 10% SOC to 90% SOC, which is the second predetermined charging range of 60% SOC (80% SOC−20% SOC) to 80% SOC (90% SOC−10% SOC). This allows the energy conversion unit  102  and/or the energy storage unit  104  to operate efficiently since the energy storage unit  104  can be charged to increase the SOC when it is efficient to do so and be depleted to decrease the SOC level when it is efficient to do so. Referring back to  FIG. 4 , the engine  128  and/or the generator  126  can operate at the point  142  when it is more efficient to do so, operate at the point  140  when it is more efficient to do so, or not at all with, for example, the engine  128  off. 
     For example, in certain situations it may be more efficient for the engine  128  and/or the generator  126  to operate at the point  142  without the use of the energy conversion unit  132  to move the automobile  100 . In other situations, it may be more efficient to operate the engine  128  and the generator  126  at the point  140  with the use of the energy conversion unit  132  to move the automobile  100 . In the extended charging mode, the energy conversion unit  102  including the engine  128  and/or the generator  126  can dynamically operate at different levels in the region  138  to ensure a more efficient overall operation of the automobile  100 . 
     In the forced charging mode, the conversion unit  102  charges the energy storage unit  104  to actively increase the SOC level until a predetermined charge limit, and thereafter maintains the SOC level of the energy storage unit  104  at substantially the predetermined charge limit. The predetermined charge limit can be, for example 80% SOC. However, the predetermined charge limit can be any percentage of SOC. In one embodiment, the predetermined charge limit is less than 100% SOC, to allow for natural recharging situations, such as during regenerative braking. In another embodiment, the SOC level of the energy storage unit  104  may be increased even when it may be inefficient to do so for the overall operation of the automobile  100 . For example, referring back to  FIG. 4 , the engine  128  and/or the generator  126  may operate at the point  142  instead of the point  140  in order to charge the energy storage unit  104  even when it may be more efficient to operate the engine  128  and the generator  126  at the point  140  or be inactive and utilize the energy conversion unit  132 . This may be beneficial, for example, when the user wishes to have a higher SOC level in the energy storage unit  104 . 
     The user selection unit  108  is connected to the control unit  106 . The user selection unit  108  can receive user input regarding operational preferences of the automobile  100  and provide the user input to the control unit  106 . The user selection unit  108  can be, for example, buttons, a keyboard, voice capture and translation devices, image capturing and translation devices, video capturing and translation devices, joysticks, or any other type of devices capable of capturing user preferences. The user selection unit  108 , for example, can receive user input indicating which mode the user wishes to operate the automobile  100 . For example, the user selection unit  108  can receive user input indicating that the user wishes to operate the automobile  100  in either the default mode, the extended charging mode, and/or the forced charging mode. 
     The global positioning system  110  is connected to the control unit  106 . The global positioning system  110  can receive global positioning system signals. The global positioning system  110  can use the global positioning system signals to determine a location of the automobile  100  and provide positioning data to the control unit  106 . The positioning data can indicate, for example, a location of a target location, a location of the automobile, and/or a distance between the target location and the automobile. 
     Furthermore, the global positioning system  110  can also provide characteristic information of the target location and/or the location of the automobile to the control unit  106 . For example, the characteristic information can include any operational requirements of the target location and/or the location of the automobile. The target location can require, for example, that the automobile  100  operate in certain modes in order to preserve and/or improve air quality. In addition, the characteristic information could include, for example, a lack of charging stations in the target location. 
     Furthermore, the positioning data and the characteristic information can be used by the control unit  106  to determine the operation mode for the energy conversion unit  102  and/or the energy storage unit  104 . For example, the control unit  106  can use the positioning data and/or the characteristic information to determine whether the energy conversion unit  102  and/or the energy storage unit  104  should be operating in the default mode, the extended charging mode, or the forced charging mode. 
     The control unit  106  is connected to the energy conversion unit  102 , the energy conversion unit  132 , the energy storage unit  104 , the user selection unit  108 , and/or the global positioning system  110 . The control unit  106  can include, for example, one or more processors located in a single location or multiple locations. The one or more processors can communicate with each other and cooperate to function as the control unit  106 . The control unit  106  can determine the charging mode of the energy conversion unit  102  and/or the energy storage unit  104  and switch charging modes of the energy conversion unit  102  and/or the energy storage unit  104  when appropriate. For example, when the automobile is first started, the control unit  106  could indicate to the energy conversion unit  102  and/or the energy storage unit  104  that it should operate in the default mode. 
     However, upon user input signifying a desire to operate in an extended charging mode, or a forced charging mode, the control unit  106  can indicate to the energy conversion unit  102  and/or the energy storage unit  104  that it should operate in the extended charging mode, or the forced charging mode. Likewise, upon user input signifying a desire to change modes based upon positioning data, the control unit  106  can indicate to the energy conversion unit  102  and/or the energy storage unit  104  to operate in the default mode, the extended charging mode, or the forced charging mode based upon the positioning data. 
     The SOC level of the energy storage unit  104  when the energy storage unit  104  and/or the energy conversion unit  102  are operating under different modes can be seen in  FIG. 5 . As seen in  FIG. 5 , the line  112  represents the SOC of the energy storage unit  104 . When the automobile is first started, the energy conversion unit  102  and/or the energy storage unit  104  are operating under the default mode and thus the automobile operates in the charge depletion mode, and then the charge sustaining mode. 
     Therefore, the control unit  106  instructs the energy storage unit  104  and/or the energy conversion unit  102  to operate in the charge depletion mode as seen in portion  114  of the line  112  when the automobile first starts, until the SOC of the energy storage unit  104  reaches a predetermined minimum charge threshold. In  FIG. 5 , the predetermined minimum charge threshold is, for example, a SOC level of 20% SOC, but can be any percentage which is sufficient to safely run the automobile. 
     Once the predetermined minimum charge threshold is reached, the control unit  106  instructs the energy conversion unit  102  and/or the energy storage unit  102  to operate in the charge sustaining mode as seen in the portion  116  of the line  112 . As can be seen, in the charge sustaining mode, the SOC level of the energy storage unit  104  is maintained at a relatively constant level at approximately 20% SOC within a first predetermined charging range. The first predetermined charging range can be, for example 10% SOC to 15% SOC. 
     The control unit  106  can also receive user input signifying a desire to change modes to an extended charging mode, or a desire to change modes based upon positioning data. Thus, when the positioning data indicates that the mode should be the extended charging mode or the user input indicates that the mode should be the extended charging mode, the control unit  106  can instruct the energy storage unit  104  and/or the energy conversion unit  102  to operate at the extended charging mode as seen in the portion  118  of the line  112 . 
     During the extended charging mode, the SOC of the energy storage unit  104  is increased or decreased based upon the conditions of the automobile. For example, the SOC of the energy storage unit  104  is increased when it is efficient to do so and the SOC of the energy storage unit  104  is decreased when it is efficient to do so. This allows the SOC to vary so that the energy conversion unit  102  and/or the energy storage unit  104  can operate more efficiently. Thus, the automobile  100  can operate more efficiently and improve, for example, a trip efficiency. 
     As seen in  FIG. 5 , the extended charging mode can vary the SOC in the second predetermined charging range, from SOC levels of 20% SOC to 80% SOC. Thus, in  FIG. 5 , the second predetermined charging range is between SOC levels 20% SOC to 80% SOC, or a second predetermined charging range of 60% SOC. Although the second predetermined charging range is 60% SOC in  FIG. 5 , the second predetermined charging range can be any number greater than the first predetermined charging range such that the energy conversion unit  102  and/or the energy storage unit  104  can operate more efficiently. The variation in the SOC during the extended charging mode allows the SOC of the energy storage unit  104  to be increased or decreased based on efficiency as opposed to being forced to increase when it is inefficient to do so, or being forced to decrease when it is inefficient to do so. Thus, the SOC during the extended charging mode can be increased or decreased based on an efficiency of the automobile  100 , such as a trip efficiency of the automobile  100 . 
     The control unit  106  can also receive user input signifying a desire to change modes to a forced charging mode, or a desire to change modes based upon positioning data and/or the characteristic information. Thus, when the positioning data and/or the characteristic information indicates that the mode should be the forced charging mode or the user input indicates that the mode should be the forced charging mode, the control unit  106  can instruct the energy storage unit  104  and/or the energy conversion unit  102  to operate at the forced charging mode as seen in the portion  120  of the line  112 . 
     During the forced charging mode, the SOC of the energy storage unit  104  is increased until it reaches the predetermined charge limit, which is 80% SOC in  FIG. 5 . This allows the user to have a substantially larger reserve of charge in the energy storage unit  104 . This can be beneficial, for example, if the user is a predetermined distance from an area where the user must be in charge depletion mode and the user needs to expend the SOC in the energy storage unit  104  to only move the automobile  100  using the energy conversion unit  132  instead of the energy conversion unit  102 . For example, a city may be particularly concerned about emissions and may require that all vehicles passing through the city operate in the charge depletion mode and turn off the engine  128  and/or the generator  126  in the energy conversion unit  102 . This can also be beneficial if there will be no charging stations in the target location. 
     In one embodiment, the present invention is a process according to  FIG. 6 . In Step S 602 , the automobile is operated in a default charging mode. For example, the energy storage unit  104  and/or the energy conversion unit  102  can operate in the default charging mode, such as the charge depletion mode, and/or the charge sustaining mode. In Step S 604 , the automobile is operated in an extended charging mode. For example, the energy storage unit  104  and/or the energy conversion unit  102  can operate in the extended charging mode. In Step S 606 , the automobile is operated in the forced charging mode. For example, the energy storage unit  104  and/or the energy conversion unit  102  can operate in the forced charging mode. 
     In Step S 608 , a global positioning system signal is received. For example, the control unit  106  can receive a GPS signal from the GPS  110 . In Step S 610 , a distance to a target location can be determined using the global positioning system signal. For example, the control unit  106  can determine a distance to a target location, such as a desired city, using the GPS signal to determine positioning data. In Step S 612 , the automobile is operated in the default charging mode, the extended charging mode, or the forced charging mode based on the distance to the target location. For example, depending on how close the automobile is to the target location, the control unit  106  can operate the automobile  100  in the default charging mode, the extended charging mode, or the forced charging mode. 
     Thus, the automobile  100  could be operating in the default charging mode or the extended charging mode, but when the distance to the target location is less than a predetermined distance, the automobile  100  could switch to the forced charging mode. The control unit  106  could also operate the automobile  100  in the default charging mode, the extended charging mode, or the forced charging mode depending on the characteristic information of the target location. This can be beneficial, if the target location is a location which restricts operation of the engine  128  and/or the generator  126  in the energy conversion unit  102 , and requires, for example, the automobile  100  to operate at the charge depletion mode. 
     Those of ordinary skill would appreciate that the various illustrative logical blocks, modules, and algorithm steps described in connection with the examples disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. Furthermore, the present invention can also be embodied on a machine readable medium causing a processor or computer to perform or execute certain functions. 
     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 artisans may 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 disclosed apparatus and methods. 
     The various illustrative logical blocks, units, modules, and circuits described in connection with the examples disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (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 may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., 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. 
     The steps of a method or algorithm described in connection with the examples disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The steps of the method or algorithm may also be performed in an alternate order from those provided in the examples. A software module may 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 known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an Application Specific Integrated Circuit (ASIC). The ASIC may reside in a wireless modem. In the alternative, the processor and the storage medium may reside as discrete components in the wireless modem. 
     The previous description of the disclosed examples is provided to enable any person of ordinary skill in the art to make or use the disclosed methods and apparatus. Various modifications to these examples will be readily apparent to those skilled in the art, and the principles defined herein may be applied to other examples without departing from the spirit or scope of the disclosed method and apparatus. The described embodiments are to be considered in all respects only as illustrative and not restrictive and the scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.