Abstract:
An improved smart antenna reception method and devices are provided that determine when to select a new antenna configuration in a multiple antenna configuration system. One embodiment attempts to eliminate unneeded configuration searching. Unneeded configuration searching can degrade overall signal quality and system performance. Configuration changing can be minimized by determining that a signal quality received from a first antenna configuration is below a threshold and changing antenna configuration. After changing antenna configuration, if the signal quality received from the second antenna configuration is lower than the signal quality received from the first antenna configuration the threshold can be lowered. By lowering the threshold, the probability of additional configuration changing can be reduced.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to mobile communication devices, and more particularly to selecting antenna configurations in a mobile communication device. 
     BACKGROUND OF THE INVENTION 
     Users of mobile communication devices, such as cellular telephones, Personal Digital Assistants (PDAs) or laptop computers that include wireless capability, etc., often experience performance problems, such as dropped calls, poor call quality, and an inability to connect with the network. Such problems are often the result of interference from other wireless signals in the area. Additionally, however, such problems are often the result of what is called multipath interference. 
     The term multipath is a term that describes how a signal transmitted in a wireless environment travels along multiple paths from the transmission source to the destination or receiver. For example, when a base station transmits a signal to a mobile communication device, the energy comprising the signal spreads out. Some of the energy can travel along a direct line to the mobile communication device. This direct line is one path. Some of the energy can, e.g., reflect off a building and then reach the mobile communication device. The reflected signal path being a second path. Similarly, some of the energy can reflect off other buildings, mountains, or other structures before reaching the mobile communication device. The different paths traveled by the signal energy from the base station to the mobile device are referred to as multipaths, and the associated signal energies are referred to as the multipath signals, or sometimes multipath for short. 
     The multipath signals combine with each other in the mobile communication device receiver. At times the multipath signals will combine constructively, but at other times the signals will combine destructively, i.e., the signals will combine in such a manner that they at least partially cancel each other out, or interfere with each other. This is because the multipath signals can be out of phase with each other due to the different lengths of the paths traveled. Destructive multipath combining, or interference, can lower the signal-to-noise ratio in the receiver, and affect other signal parameters, causing the problems referred to above. Such destructive multipath interference is often referred to as fading, i.e., it causes the signal as seen by the mobile communication device receiver to fade out. 
     Spatial diversity has been used to combat the problem of destructive multipath interference, or fading. In its simplest form, spatial diversity comprises two antennas spaced a certain distance apart. The distance between the antennas should be related to the wavelength of the signal being received, e.g., a multiple or sub-multiple of the wavelength. The idea of spatial diversity is that the distance between the antennas allows each antenna to receive samples of the signal independent of the other antenna. While the signal at one antenna might be experiencing destructive interference, the signal at the other might be experiencing constructive interference. 
     The difference in position of the antennas will affect the phase of the multipath signals. The effect of the different path lengths can affect the phase of the multipath signals enough such that multipath signals that would have combined destructively at the first antenna, will now combine constructively at the second antenna. Thus, spatial diversity can improve performance and help overcome, e.g., the problems referred to above. Moreover, spatial diversity can extend to any number of antennas. 
     A mobile communication device can, therefore, be configured with a plurality of antennas and a means for changing between antennas when the received signal quality is degraded beyond a certain point, which can for example be measured in terms of received signal power. Accordingly, the mobile communication device can be configured to monitor the signal power of a signal received using a first antenna of a plurality of antennas. When the received signal power drops below a certain threshold, then the device can be configured to switch to another antenna that exhibits higher received signal power. 
     Since mobile communications devices are typically not large enough to implement true spatial diversity, polarization diversity can be implemented in order to improve performance in a mobile communication device. The polarization diversity case is similar to the spatial diversity case. Whereas spatial diversity relies on the separation of the antenna to get independent samples, polarization diversity relies on the different polarizations. For example a vertically polarized antenna will tend to see vertically polarized signals and tend to reject horizontally polarized signals; therefore, samples from a vertically polarized antenna will tend to be independent from samples from a horizontally polarized antenna. Spatial diversity can also be combined with polarization diversity, as in the case where a vertically polarized antenna and a horizontally polarized antenna are included in the same device. Because the two antennas are typically located at different locations within the device, they will exhibit at least some degree of spatial diversity. 
     Thus, a plurality of antennas can be incorporated into a communication device that comprises spatial diversity, polarization diversity, or both, such that the device can switch between different antennas and/or different polarizations in order to attempt to improve the received signal quality. 
     A smart antenna system is an antenna system that is capable of steering the antenna beam or is capable of beam forming. Examples of types of smart antennas would include a single active element with parasitic elements. By modifying the characteristics of the parasitic elements the beam can be steered, shaped, or both. Another example smart antenna can include multiple active elements where the phase of the signal between the elements can be changed to cause the beam to steer or change shape. Alternatively, a smart antenna can include multiple active elements that allow the signals to be applied to each independently and weighted to steer or form the beam. Processing for these smart antennas can, for example, be done in DSP. 
     In conventional devices, the device must check each antenna to determine if there is an antenna with better signal quality than the current configuration. Unfortunately, this can actually degrade device performance even further, since often many if not all of the other configuration will have worse signal quality than the current configuration. Thus, the device can spend significant time searching configuration that actually have worse performance than the current configuration, which degrades the device&#39;s overall performance during the searching period. 
     SUMMARY OF THE INVENTION 
     A mobile communication device comprising a plurality of antenna configurations is configured to selectively search the plurality of antenna configurations in order to reduce the likelihood that an antenna configuration exhibiting worse received signal quality than a current configuration will be searched, when the signal quality for the current configuration drops below a certain threshold. A threshold is associated with each configuration. Accordingly, when the signal quality for the current configuration drops below a certain threshold, then other configurations will be searched to determine if they exhibit better signal quality. If the searched configurations actually exhibit lower signal quality, then the threshold for this configuration can be altered making it less likely that the configuration will be searched in the future. 
     These and other features, aspects, and embodiments of the invention are described in greater detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a diagram illustrating an example mobile communication device configured in accordance with one embodiment; 
         FIG. 2  is a flowchart illustrating an example method for changing antenna configurations using the mobile communication device of  FIG. 1 ; 
         FIG. 3  is a flow chart illustrating another example method for changing antenna configurations using the mobile communication device of  FIG. 1 ; 
         FIG. 4  is a flowchart illustrating an example method for changing antennas in the mobile communication device of  FIG. 1  that uses timers in accordance with one embodiment; 
         FIG. 5  is a flowchart illustrating another embodiment that uses timers as part of the method for changing antenna configurations in a mobile communication device with multiple antennas; and 
         FIG. 6  is a flowchart illustrating another embodiment of a method for changing antenna configurations in a mobile communication device with multiple antennas. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a diagram illustrating an example mobile communication device  100  configured in accordance with one embodiment of the systems and methods described herein. For purposes of this discussion, it is assumed that mobile communication device  100  is a cellular telephone; however, it will be understood that the systems and methods described herein can apply to other types of mobile communication devices, such as PCS telephones, PDAs or laptops with wireless capability, or any other type of mobile communication device that uses an antenna to receive wireless signals. 
     Wireless communication device  100  comprises a plurality of antennas. For ease of discussion, wireless communication device  100  is shown to comprise two antennas  102  and  104 ; however, it will be clear, and will be discussed in more detail below, that any number of antennas can be included in device  100 . Antennas  102  and  104  are configured to transmit and receive wireless signals. Antennas  102  and  104  are illustrated extending external to device  100 . In other embodiments, however, one or both antennas can be internal to device  100 . Further, as can be seen, antennas  102  and  104  are separated by space (A). Depending on the embodiment, (A) can be a multiple or sub-multiple of the wavelength of the wireless signals received by antennas  102  and  104 . 
     Antennas  102  and  104  are interfaced with a switch, or multiplexer (MUX)  106 . MUX  106  is configured to interface one of antennas  102  or  104  with radio receiver  108 , depending on the position, or settings, of MUX  106 . The settings of MUX  106  are controlled by processor  110  as described below. 
     Radio receiver  108  comprises the functional components required to receive wireless radio signals via antennas  102  and  104 . Thus, radio receiver  108  can comprise the circuits required to convert a radio signal received via antennas  102  or  104  into a baseband signal that can be processed by processor  110 . It will be apparent that device  100  can also comprise a radio transmitter (not shown) that can comprise the circuitry necessary to convert a baseband signal produced by processor  110  into a radio signal that can be transmitted by antennas  102  or  104 . Such a radio transmitter may or may not be interfaced with MUX  106 . In general, it will be clear that device  100  comprises other known functional components, which will not be described here for the sake of brevity; however, the components illustrated in  FIG. 1  should not be seen as limiting the embodiments described herein to any particular functional architecture or configuration. 
     Processor  110  comprises the functional components necessary to encode baseband signals for transmission and decode baseband signals received and produced by radio receiver  108 . In addition, processor  110  can comprise the functional components necessary to control the operation of device  100 . Thus, processor  110  can comprise the required hardware and software for performing the tasks described below, in particular controlling MUX  106 . Processor  110  can actually comprise multiple devices and/or processing circuits, such as Digital signal Processors (DSPs), audio processors, math coprocessors, microcontrollers, microprocessors, etc. 
     Device  100  also comprises memory  114  configured to store instructions that can be accessed by processor  110 . The instructions provide processor  110  with the instructions needed to control the operation of device  100  and perform the operations described below. Memory  114  can also be configured to store temporary and permanent date used by processor  110  to carry out the instructions stored in memory  114 . 
     Memory  114  can actually comprise multiple memory devices. For example, a typical cellular telephone comprises a Flash based memory device for storing operating instructions as well as a Static RAM (SRAM) device for storing variables and data required by the instructions. Cellular telephones will also often comprise an Electrically Erasable and Programmable ROM (EEPROM) device. All or some of these multiple memory devices can be incorporated into a single device or package. For example, in cellular telephones, the Flash and SRAM are often integrated into a single package. Alternatively, some or all of the memory devices can be included in separate devices or packages. 
     Processor  110  can be configured to monitor the quality of signals received via antennas  102  or  104  and radio receiver  108  and determine when the quality has dropped below a preferred threshold. When the signal quality drops below the preferred threshold, processor  110  can be configured to cause MUX  106  to switch from the antenna that is currently interfaced with radio receiver  108  to the other. Processor  110  can then check the signal quality for signals received by this antenna in order to determine whether the signal quality is better for this antenna than the previous one. 
     This process is described for the simple example of two antennas in the method of  FIG. 2 . It should be noted than in addition to being spatially diverse, antennas  102  and  104  can also comprise different polarizations. The combination of position and polarization can be referred to as an antenna configuration. Thus, when processor  110  causes MUX  106  to switch, the switch can be referred to as a switch from one antenna configuration to another. Thus, the term antenna configuration will be used in the following discussion; however, this should not be seen as excluding the situation where the two antennas are simply spatially diverse. Further, while antenna configurations can include discrete configurations, i.e., changing from one discrete configuration to another, as in the example above, antenna configurations can also be ranges of solutions. For example, in one embodiment an antenna pattern can be shaped such that the antenna pattern can be pointed in any direction, not just some number of predetermined directions, by adjusting the relative phase between the antenna elements. In this embodiment, MUX  106  can be replaced by an antenna configuration control. The antenna configuration control can steer or point the antenna or select an antenna configuration from a plurality of antenna configurations. 
     In the process of  FIG. 2 , it will be assumed that device  100  is using antenna  102  to receive wireless signals. In step  202 , processor  110  determines that the signal quality for signals being received via antenna  102  is below a threshold. In step  204 , processor  110  can control MUX  106 , via control line  112 , to switch from the antenna configuration of antenna  102  to the configuration of antenna  104 . Once the switch has occurred, processor  110  can assess, in step  206 , whether the signal quality for signals being received using the configuration of antenna  104  is worse than the signal quality for signals received using the antenna configuration of antenna  102 . 
     If the signal quality is not worse, i.e., the signal quality for the new configuration is better than of the old configuration, then processor  110  can be configured to continue the use of the new configuration, i.e., configuration  104 . The process can then start over, with processor  110  determining whether the received signal quality using configuration  104  drops below a certain threshold in step  202 . If on the other hand, the signal quality for configuration  104  is worse than the signal quality for configuration  102 , then processor  110  can control MUX  106  via control line  112  to switch back to the configuration of antenna  102 . 
     Once processor  110  has caused MUX  106  to switch back, processor  110  can update the threshold used in step  202 . For example, the threshold can be a value or set of values stored in memory  114 . Processor  110  can, for example, lower the threshold being used in step  202 . The lower threshold should make it less likely that processor  110  will cause the antenna configuration to switch in step  204 , because the signal quality will be less likely to drop below the new threshold. Once the threshold is altered in step  210 , then the process can revert to step  202 , where processor  110  can determine whether the signal quality for signals received via antenna configuration  102  has dropped below the new threshold. 
     It will be clear that different thresholds can be used and that in some embodiments, processor  110  will be checking, in step  202 , to determine whether a threshold has been exceeded. Further, processor  110  can be configured to raise such a threshold in step  210 . 
     Processor  110  can be configured to determine signal quality using a variety of parameters and/or combination of parameters. As mentioned above, receive signal strength or power can be used by processor  110  in step  202 . In addition, however, other parameters such as signal-to noise ratio, Signal Error Rate (SER), Bit Error Rate (BER), Frequency Error Rate (FER), or some subset or combination thereof can be used. Processor  110  can be configured to determine such parameters internally. In other embodiments, such parameters can be determined external to processor  110 , e.g., in radio receiver  108 , and communicated to processor  110 . 
     The amount of time that device  100  spends changing antenna configurations and checking signal quality for the new configuration is reduced, by altering the threshold in step  210  to make it less likely that processor  110  will determine that the threshold has been crossed in step  202 . This can result in improved performance, since it has already been determined in step  206  that the alternative antenna configuration is actually experiencing worse signal conditions. In effect, the process of  FIG. 2  adds hysteresis to the changing process to avoid the condition where processor  110  is constantly causing the antenna configuration to be switched back and forth. 
     In certain embodiments, device  100  can also include a timer that can be used to define a time period for which the altered threshold of step  210  will be used. Since device  100  is a mobile device and will often be moving, the signal conditions for the various antenna configurations will likely change over time and the signal conditions for the alternative antenna configuration, or configurations, can become better. Using a timer ensures that these other configurations are checked at least periodically. Other embodiments that use a timer, or timers, will be discussed more fully below. 
       FIG. 3  is a flowchart illustrating an example method for changing antenna configurations in a mobile communication device with multiple antennas in accordance with one embodiment of the systems and methods described herein. Here, threshold values are set to default values in step  302 . The default values can, for example, be predetermined and preset when the communication device is manufactured. Such preset values can then be stored, e.g., in memory  114 . In step  304 , processor  110  can be configured to select an initial antenna configuration. Processor  110  can be configured to then monitor the received signal quality and determine whether it falls below a threshold in step  304 . If the current signal quality is not below the threshold, then the process can revert to step  304  in which processor  110  continues to monitor the received signal quality. 
     When the signal quality for the current antenna configuration falls below a threshold value, then processor  110  can be configured to cause MUX  106  to switch to each of the alternate antenna configurations in succession and to check the received signal quality for each alternate antenna configuration in step  306 . The antenna configuration with the best signal quality among the antenna configurations searched can then be selected in step  308 . In step  310 , processor  110  can be configured to determine whether the selected configuration has better or worse signal quality than the original configuration. If the signal quality for the selected configuration is worse than the signal quality for the original configuration, then in step  314 , processor  110  can lower the threshold used in step  304  and cause the original antenna configuration to be maintained in step  316 . 
     Lowering the threshold will reduce the likelihood that processor  110  will cause the other antenna configurations to be searched. Again, this can actually improve performance, since it has already been determined that all other configurations have worse signal quality than the current configuration. In other embodiments, some of which are discussed below, multiple thresholds can be used and altered to reduce the likelihood that some groups of antenna configurations will be searched more, while maintaining the same likelihood for other groups, or altering the likelihood for other groups differently. 
     In step  312 , processor  110  can cause the selected configuration to replace the current configuration when it is determined that the signal quality for the selected configuration is better than the signal quality for the current configuration. The process can then resume at step  304  where processor  110  can monitor the signal quality for the new configuration to determine whether it drops below the threshold. It should be noted that in addition to improving receiver performance, the improved receiver performance can also improve the forward link system capacity by reducing the base station resources allocated to each mobile. Additionally, in wireless systems, mobile communication devices are often handed off from one base station to another as they move throughout the system. In one embodiment, the threshold values can be reset, e.g., to a default value, each time a device undergoes such a handoff. In certain embodiments, the default values for each base station can actually be downloaded to the device upon handoff. In other embodiments, the default values can simply be stored and maintained on the device, e.g., in memory  114 . 
       FIG. 4  is flow chart illustrating an example method for selecting an antenna configuration that uses timers in accordance with the systems and methods described above. The use of a timer, or timers, was briefly referred to above. As with the methods of  FIGS. 2 and 3 , the method  FIG. 4  begins in step  402  with the signal quality for signals being received using a current antenna configuration being monitored, e.g., by processor  110 . Processor  110  then determines whether the signal quality has dropped below a certain threshold in step  404 . If the signal quality is not below the threshold, then processor  110  can continue to monitor the signal quality in step  402 . 
     If, on the other hand, the signal quality has dropped below the threshold, then in step  406 , processor  110  can select another antenna configuration in step  406  to determine, in step  408 , whether the other configuration provides better or worse signal quality. If the other configuration exhibits better signal quality, then in step  410  processor  110  can switch to the other antenna configuration and the process can continue in step  402 . 
     If the signal quality for the other antenna configuration is worse than the signal quality for the original antenna configuration, as determined in step  408 , then processor  110  can activate a timer in step  412 . The process will then continue on step  402  with the signal quality for the original antenna configuration being monitored and other antenna configurations being selected (step  406 ) when the signal quality drops below the threshold (step  404 ); however, once the timer is activated, in step  412 , then the associated antenna configuration, which was selected in step  406  and determined to provide worse signal quality in step  408 , can be excluded from the process for the time period defined by the timer. Use of the timer will ensure that the associated antenna configuration is not searched for at least the time period defined by the timer. This can improve receiver performance, since it has already been determined that the antenna configuration does not improve signal quality. If each configuration is associated with a timer, then other antenna configuration will not be affected. Thus, they can continue to be searched unless it is determined that these other configurations provide worse signal quality. Alternatively, the antenna configuration with the best signal quality can be selected in step  406 . In such embodiments, if it is determined that the signal quality for this antenna configuration is worse than the signal quality for the original antenna configuration, then the timer can be used to prevent any of the antenna configurations from being selected for the period defined by the timer, since it has been determine that none of them exhibit better signal quality than the current configuration. In still another embodiment, a group, or groups of antennas can be excluded for the time period defined by the timer, while others are not. Obviously, the timer, or timers can be configured to count up or down, depending on the embodiment. 
     Still another embodiment using timers is illustrated in  FIG. 5 . In this embodiment, a timer is associated with each possible antenna configuration. The signal quality for all antenna configurations can be determined in step  502 . The length, or time, associated with each of the timers can then be altered, or set, in step  504 , based on the signal quality determined for the associated antenna configurations. The timers can then be activated in step  506 . The antenna configuration with the best performance can be selected in step  508  and be used to receive signals. The signal quality for that selected antenna configuration can then be monitored as before in step  510 . 
     Each of the other antenna configurations will be excluded for a time period that is related to the signal quality associated with the antenna configuration and defined by the associated timers. Of course, some antenna configurations may not be excluded. The process of  FIG. 5  assures that all antenna configurations will eventually be searched but that some will be searched more often. 
     If the monitored signal level does drop below a certain threshold, then all of the antenna configurations can be checked again to see if one has better signal quality. In addition, depending on the embodiment, the timers can be reset with new values at this time. 
       FIG. 6  is a flowchart  600  illustrating an embodiment that uses timers and thresholds as part of the method for changing antennas in a mobile communication device with multiple antennas. Antenna configurations can be grouped based on the signal quality received at each antenna. Timers can be used so that the method does not have to search all of the antenna configurations when the signal quality falls below a threshold. 
     In step  602 , each antenna configuration can be initialized with default threshold values. The current antenna configuration can then be monitored in step  604 . In step  606 , it can be determined whether the signal quality for the current configuration has dropped below a threshold. In addition, a timer, i.e., timer  1 , can be set. If it is determined in step  606  that the signal quality is not below the threshold, then timer  1  can be checked to see if it has expired in step  608 . If timer  1  has not expired, then the signal quality can continue to be monitored in step  604 . 
     If timer  1  has expired, in Step  608 , or if the signal quality is below the threshold as determined in step  606 , then all of the alternative antenna configurations can be searched beginning in step  610 . Use of timer  1  in this fashion allows other antenna configurations to be searched periodically, even if the signal quality for the current antenna configuration does not go below the threshold. Since the default threshold needs to be selected based on network configurations and the location of the mobile communication device, it is not always practical to select one default threshold that would work well for all network configurations. Adding a timer, i.e., timer  1 , allows other antenna configurations to be searched. The time period associated with timer  1  can vary depending on the requirements of a particular implementation. For example, in certain implementations, it can be undesirable to change antenna configurations, or at least undesirable to change them often. In such embodiments, the length of timer  1  can be made longer. It can also be possible, depending on the embodiment, to update the default thresholds based on the requirements of a particular implementation. For example, in certain embodiments, data from past experience can be used to determine a more optimal default threshold and timer value. 
     In step  610 , the other antenna configurations can be searched and, in step  620 , the threshold can be calculated and the antenna configurations can be grouped. The idea is to partition the antenna configurations into multiple groups, e.g., based on signal quality so that not all the antenna configurations need to be searched when comparing against a threshold. For example, only antenna configurations belonging to group  1  need to be searched and compared against threshold  1 . 
     In step  612 , timer  2  and timer  3  can be reset. In the embodiment of  FIG. 6 , multiple thresholds can actually be used. Thus, in step  614 , it can be determined if the signal quality, as determined in step  606 , is below a first threshold. If the signal quality is above the first threshold, then all antenna configurations associated with this threshold can be searched in step  616 . In step  618 , it can be determined whether the signal quality for any of the antenna configurations in this group is better than the signal quality determined in step  606  for the current antenna configuration. 
     If it is determined in step  618 , that the signal quality for an antenna configuration in this group is better than the signal quality for the current antenna configuration, then this antenna configuration can be selected in step  642 . In addition, however, a second timer (timer  2 ) can also be used and can be checked in step  638  to determine if it has expired. If it has expired, then all of the antenna configurations can be searched again in step  610  and the timers reset in step  612 , instead of selecting the alternative configuration in step  642 . Use of timer  2  in this fashion prevents excessive antenna configuration changes. 
     It should also be noted that in addition to changing the antenna configuration in step  642 , all or some of the threshold values can be recalculated. In addition, the transmit power can be monitored to ensure that changing antenna configurations will not cause the maximum transmit power for the mobile communication device to be exceeded. The signal quality for the new antenna configuration can then be monitored. 
     If it is determined, in step  618 , that none of the alternative antenna configurations in the group associated with the first threshold provides better signal quality than the current antenna configuration, then a third timer (timer  3 ) can then be checked to determine if it has expired. If timer  3  has expired, then all of the antenna configuration can be checked in step  610 , regrouped at  620  and the timers reset in step  612 . If the signal quality is above the new threshold  1 , then all antenna configurations associated with this threshold can be checked in step  616 . Timer  3  can be included to prevent an “infinite loop” scenario whereby if the 3 thresholds are chosen too high, the signal quality for the current antenna configuration will never fall below any of the thresholds and none of the other antenna configurations will be searched. 
     If, at any point, it is determined that the signal quality is not above threshold  1  in step  614 , then the other threshold values can be checked, e.g. in step  622  and  630 . If the signal quality is above one of these other threshold values, then all the associated antenna configurations can be checked, e.g., in steps  624  and  632 , and it can be determined if the signal quality is better for any of these other antenna configurations, e.g., in steps  626  and  634 . If the signal quality is not better for any of these other antenna configurations, then timer  3  can be checked in step  640 . If the signal quality is better for any of these alternative configurations, then timer  2  can be checked and, depending on the status of timer  2 , the alternative configuration with better signal quality can be selected (step  642 ) or all of the antenna configurations can be searched again (step  610 ). 
     It should be noted that each alternative antenna configuration can have its own threshold. Thus, if there are N antenna configurations, and therefore N−1 alternative antenna configurations, then there can be N−1 thresholds to be checked in steps  614 ,  622 ,  630 , etc. Alternatively, the number of thresholds used can be reduced by ranking and grouping the antenna configurations. In other words, if it is determined, e.g., in step  610 , that several of the antenna configurations exhibit similar signal quality, and then they can be grouped and assigned the same threshold. This can further limit the amount of time that the device spends searching alternative configurations, which as explained can actually reduce performance. 
     As mentioned above, the determination of the signal quality for a given antenna configuration can be based on a plurality of parameters. In certain embodiments, a combination of all or some of these parameters can be used to determine the signal quality. Moreover, these parameters can include forward link as well as reverse link parameters. In certain embodiments, the parameters can be weighted and then combined. The weighting can even vary in certain embodiments, e.g., depending on whether the device is engaged in data or voice communication. In the case of data communication, the Quality of Service (QoS) and forward and reverse link data rates can also be parameters that can be used to determine the signal quality and/or the appropriate weighting associated with various parameters. 
     While certain embodiments of the inventions have been described above, it will be understood that the embodiments described are by way of example only. Accordingly, the inventions should not be limited based on the described embodiments. Rather, the scope of the inventions described herein should only be limited in light of the claims that follow when taken in conjunction with the above description and accompanying drawings.